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BibTeX-Key	Author / Editor / Organization	Title	Year	Journal / Proceedings / Book	BibTeX type	Keywords
Anderson1994	Anderson, P.; Bartlein, P. & Brubaker, L.	Late Quaternary history of tundra vegetation in northwestern Alaska [Abstract] [BibTeX]	1994	Quaternary Research Vol. 41 (3) , pp. 306-315	article
Abstract: Pollen analysis of a new core from Joe Lake indicates that the late Quaternary vegetation of northwestern Alaska was characterized by four tundra and two forest-tundra types. These vegetation types were differentiated by combining quantitative comparisons of fossil and modern pollen assemblages with traditional, qualitative approaches for inferring past vegetation, such as the use of indicator species. Although imprecisely dated, the core probably spans at least the past 40,000 yr. A graminoid-Salix tundra dominated during the later and early portions of the glacial record. The middle glacial interval and the transition from glacial to interglacial conditions are characterized by a graminoid-Betula-Salix tundra. A Populus forest-Betula shrub tundra existed during the middle potion of this transition, being replaced in the early Holocene by a Betula-Alnus shrub tundra. The modern Picea forest-shrub tundra was established by the middle Holocene. These results suggest that the composition of modem tundra communities in northwestern Alaska developed relatively recently and that throughout much of the late Quaternary, tundra communities were unlike the predominant types found today in northern North America. Although descriptions of vegetation variations within the tundra will always be restricted by the innate taxonomic limitations of their herb-dominated pollen spectra, the application of multiple interpretive approaches improves the ability to reconstruct the historical development of this vegetation type. (C) 1994 University of Washington.
BibTeX: @article{Anderson1994, author = {Anderson, PM and Bartlein, PJ and Brubaker, LB}, title = {Late Quaternary history of tundra vegetation in northwestern Alaska}, journal = {Quaternary Research}, year = {1994}, volume = {41}, number = {3}, pages = {306--315} }
Anderson1991	Anderson, P.; Bartlein, P.; Brubaker, L.; Gajewski, K. & Ritchie, J.	Vegetation-pollen-climate relationships for the arcto-boreal region of North America and Greenland [Abstract] [BibTeX] [PDF]	1991	Journal of Biogeography Vol. 18 (5) , pp. 565-582	article
Abstract: We examine modern pollen, vegetation and climate relationships for the arcto-boreal region of North America using isopollen maps, scatter diagrams and response surfaces. These analyses are based on an array of 1119 modern pollen sites extending from Alaska to Greenland (excluding the Pacific-Cordillera region of western North America) and north of 42-degrees-N latitude. The pollen sum consists of thirty-one taxa selected for their abundance on the modern landscape or significance as indicators of particular vegetation types. Response surfaces were calculated using a locally weighted-average procedure in order to display the percentages of the various taxa as a function of one to three climate variables. The isopoll maps accurately reflect taxa abundance and range limits, although the actual percentage at these limits may vary. Pollen of the major boreal taxa have optima at 10-20-degrees-C and dry (Pinus), moist (Abies) and intermediate (Picea) values of precipitation. Monospecific pollen taxa and those where the species have similar ecologies show a simple climate optimum, whereas pollen taxa with several species, such as Betula, show multiple optima. Each boreal taxon, even those with similar ranges, has a unique surface, suggesting that community level responses to climatic change, whether past or future, are likely to be complex and variable throughout North America.
BibTeX: @article{Anderson1991, author = {Anderson, PM and Bartlein, PJ and Brubaker, LB and Gajewski, K and Ritchie, JC}, title = {Vegetation-pollen-climate relationships for the arcto-boreal region of North America and Greenland}, journal = {Journal of Biogeography}, year = {1991}, volume = {18}, number = {5}, pages = {565--582} }
Anderson1989	Anderson, P.; Bartlein, P.; Brubaker, L.; Gajewski, K. & Ritchie, J.	Modern analogs of Late Quaternary pollen spectra from the western interior of North America [BibTeX] [PDF]	1989	Journal of Biogeography Vol. 16 (6) , pp. 573-596	article	modern analogues
BibTeX: @article{Anderson1989, author = {Anderson, PM and Bartlein, PJ and Brubaker, LB and Gajewski, K and Ritchie, JC}, title = {Modern analogs of Late Quaternary pollen spectra from the western interior of North America}, journal = {Journal of Biogeography}, year = {1989}, volume = {16}, number = {6}, pages = {573--596} }
Arneth2010	Arneth, A.; Harrison, S.; Zaehle, S.; Tsigaridis, K.; Menon, S.; Bartlein, P.; Feichter, J.; Korhola, A.; Kulmala, M.; O'Donnell, D.; Schurgers, G.; Sorvari, S. & Vesala, T.	Terrestrial biogeochemical feedbacks in the climate system [Abstract] [BibTeX]	2010	Nature Geoscience Vol. 3 (8) , pp. 525-532	article
Abstract: The terrestrial biosphere is a key regulator of atmospheric chemistry and climate. During past periods of climate change, vegetation cover and interactions between the terrestrial biosphere and atmosphere changed within decades. Modern observations show a similar responsiveness of terrestrial biogeochemistry to anthropogenically forced climate change and air pollution. Although interactions between the carbon cycle and climate have been a central focus, other biogeochemical feedbacks could be as important in modulating future climate change. Total positive radiative forcings resulting from feedbacks between the terrestrial biosphere and the atmosphere are estimated to reach up to 0.9 or 1.5 W m(-2) K-1 towards the end of the twenty-first century, depending on the extent to which interactions with the nitrogen cycle stimulate or limit carbon sequestration. This substantially reduces and potentially even eliminates the cooling effect owing to carbon dioxide fertilization of the terrestrial biota. The overall magnitude of the biogeochemical feedbacks could potentially be similar to that of feedbacks in the physical climate system, but there are large uncertainties in the magnitude of individual estimates and in accounting for synergies between these effects.
BibTeX: @article{Arneth2010, author = {Arneth, A and Harrison, SP and Zaehle, S and Tsigaridis, K and Menon, S and Bartlein, PJ and Feichter, J and Korhola, A and Kulmala, M and O'Donnell, D and Schurgers, G and Sorvari, S and Vesala, T}, title = {Terrestrial biogeochemical feedbacks in the climate system}, journal = {Nature Geoscience}, year = {2010}, volume = {3}, number = {8}, pages = {525--532} }
Aspinall2002	Aspinall, R.; Marcus, W. & Boardman, J.	Considerations in collecting, processing, and analyzing high spatial resolution, hyperspectral data for environmental investigations [BibTeX] [PDF]	2002	Journal of Geographical Systems Vol. 4 , pp. 15-29	article	remote sensing
BibTeX: @article{Aspinall2002, author = {Aspinall, RJ and Marcus, WA and Boardman, JW}, title = {Considerations in collecting, processing, and analyzing high spatial resolution, hyperspectral data for environmental investigations}, journal = {Journal of Geographical Systems}, year = {2002}, volume = {4}, pages = {15-29} }
Barboni2004	Barboni, D.; Harrison, S.; Bartlein, P.; Jalut, G.; New, M.; Prentice, I.; Sanchez-Goni, M.; Spessa, A.; Davis, B. & Stevenson, A.	Relationships between plant traits and climate in the Mediterranean region: A pollen data analysis [Abstract] [BibTeX] [PDF]	2004	Journal of Vegetation Science Vol. 15 (5) , pp. 635-646	article	vegetation and climate
Abstract: Question: What are the correlations between the degree of drought stress and temperature, and the adoption of specific adaptive strategies by plants in the Mediterranean region? Location: 602 sites across the Mediterranean region. Method: We considered 12 plant morphological and phenological traits, and measured their abundance at the sites as trait scores obtained from pollen percentages. We conducted stepwise regression analyses of trait scores as a function of plant available moisture (alpha) and winter temperature (MTCO). Results: Patterns in the abundance for the plant traits we considered are clearly determined by alpha, MTCO or a combination of both. In addition, trends in leaf size, texture, thickness, pubescence and aromatic leaves and other plant level traits such as thorniness and aphylly, vary according to the life form (tree, shrub, forb), the leaf type (broad, needle) and phenology (evergreen, summer-green). Conclusions: Despite conducting this study based on pollen data we have identified ecologically plausible trends in the abundance of traits along climatic gradients. Plant traits other than the usual life form, leaf type and leaf phenology carry strong climatic signals. Generally, combinations of plant traits are more climatically diagnostic than individual traits. The qualitative and quantitative relationships between plant traits and climate parameters established here will help to provide an improved basis for modelling the impact of climate changes on vegetation and form a starting point for a global analysis of pollen-climate relationships.
BibTeX: @article{Barboni2004, author = {Barboni, D and Harrison, SP and Bartlein, PJ and Jalut, G and New, M and Prentice, IC and Sanchez-Goni, MF and Spessa, A and Davis, B and Stevenson, AC}, title = {Relationships between plant traits and climate in the Mediterranean region: A pollen data analysis}, journal = {Journal of Vegetation Science}, year = {2004}, volume = {15}, number = {5}, pages = {635--646} }
Bartlein1997a	Bartlein, P. Huntley, B.; Cramer, W.; Morgan, A.; Prentice, I. & Allen, J. (Hrsg.)	Past environmental changes: characteristic features of Quaternary climate variations ( Past and Future Rapid Environmental Changes: The Spatial and Evolutionary Responses of Terrestrial Biota ) [BibTeX] [PDF]	1997	NATO ASI Series Past and Future Rapid Environmental Changes: The Spatial and Evolutionary Responses of Terrestrial Biota Vol. 147 , pp. 11-29	inbook	paleoclimatic analysis and data-model comparisons vegetation and climate
BibTeX: @inbook{Bartlein1997a, author = {Bartlein, PJ}, title = {Past and Future Rapid Environmental Changes: The Spatial and Evolutionary Responses of Terrestrial Biota}, journal = {NATO ASI Series}, publisher = {NATO ASI Series}, year = {1997}, volume = {147}, pages = {11-29} }
Bartlein1982	Bartlein, P.	Streamflow anomaly patterns in the USA and southern Canada - 1951-1970 [BibTeX]	1982	Journal of Hydrology Vol. 57 (1-2) , pp. 49-63	article
BibTeX: @article{Bartlein1982, author = {Bartlein, PJ}, title = {Streamflow anomaly patterns in the USA and southern Canada - 1951-1970}, journal = {Journal of Hydrology}, year = {1982}, volume = {57}, number = {1-2}, pages = {49--63} }
Bartlein1998	Bartlein, P.; Anderson, K.; Anderson, P.; Edwards, M.; Mock, C.; Thompson, R.; Webb, R. & Whitlock, C.	Paleoclimate simulations for North America over the past 21,000 years: Features of the simulated climate and comparisons with paleoenvironmental data [Abstract] [BibTeX] [Figures] [PDF]	1998	Quaternary Science Reviews Vol. 17 (6-7) , pp. 549-585	article	paleoclimatic analysis and data-model comparisons
Abstract: Maps of upper-level and surface winds and of surface temperature and precipitation illustrate the results of a sequence of global paleoclimatic simulations spanning the past 21,000 yr for North America. We review (a) the large-scale features of circulation, temperature, and precipitation that appear in the simulations from the NCAR Community Climate Model Version 1 (CCM 1), (b) the implications of the simulated climate for the past continental-scale distributions of three plant taxa (Picea spp., Pseudotsuga menziesii. and Artemisia tridentata), which are broadly representative of the vegetation across the continent, and (c) the potential explanations in terms of atmospheric circulation or surface energy- and water-balance processes for mismatches between the simulations and observations. Most Of the broad-scale features of previous paleoclimatic simulations with the NCAR CCM 0 for North America are present in the current simulations. Many of the elements of a conceptual model (based on previous climate simulations) that describes the controls of paleoclimatic variations across North America during the past 21,000 yr are found in simulations reviewed here. These include (1) displacement of the jet stream by the Laurentide Ice Sheet to the south of its present position in both winter and summer, (2) generation of a 'glacial anticyclone' over the ice sheet at the LGM, and the consequent induction of large-scale sinking motions induced over eastern North America, (3) changes in the strength of surface atmospheric circulation features through time, including weakening of the Aleutian low in winter, and strengthening of the eastern Pacific and Bermuda high-pressure systems in summer as the ice sheet decreased in size, (4) development of a 'heat low' at the surface and a strengthened ridge in the upper-atmosphere over the continent at the time of the maximum summer insolation anomaly, (5) increases in summer temperature earlier in regions remote from the ice sheet (these increases appear earlier in the present (CCM 1) simulations than in the previous (CCM 0) ones, however), and (6) continuation of negative winter temperature anomalies into the middle Holocene. Ln general, simulated surface conditions that are discordant with paleoenvironmental observations can be attributed to the simulation of particular atmospheric circulation patterns (e.g. those that suppress precipitation or advect warm air into a region), with these mismatches amplified in Beringia and the southeastern United States by surface energy- and water-balance processes. (C) 1998 Elsevier Science Ltd. All rights reserved.
BibTeX: @article{Bartlein1998, author = {Bartlein, PJ and Anderson, KH and Anderson, PM and Edwards, ME and Mock, CJ and Thompson, RS and Webb, RS and Whitlock, C}, title = {Paleoclimate simulations for North America over the past 21,000 years: Features of the simulated climate and comparisons with paleoenvironmental data}, journal = {Quaternary Science Reviews}, year = {1998}, volume = {17}, number = {6-7}, pages = {549--585}, note = {http://geography.uoregon.edu/envchange/figures/Bartlein-etal-QSR-1998-figs/index.html} }
Bartlein1995	Bartlein, P.; Edwards, M.; Shafer, S. & Barker, E.	Calibration of radiocarbon ages and the interpretation of paleoenvironmental records [Abstract] [BibTeX] [PDF]	1995	Quaternary Research Vol. 44 (3) , pp. 417-424	article	paleoecology
Abstract: Calibration of the radiocarbon timescale of paleoecological records is essential if they are to be explained correctly in terms of their governing ecological or climatological controls, The differences between calendar ages and radiocarbon ages that arise from variations in C-14 production through time can distort the chronologies of individual records and the interpretations based on them, Misleading impressions of synchrony or diachrony of events among multiple records can result, and estimates of the apparent duration of episodes and rates of sedimentation and local population changes can be biased, Displays of the temporal patterns of migration or extinction may also be affected, Spurious correlations may arise between records with radio carbon-controlled chronologies and time series of potential controls that are expressed on a calendar time scale, Support for particular explanations of features in a paleoecological record may vary depending on whether radiocarbon ages are calibrated or not, This situation is illustrated using the eastern Beringian Populus subzone as an example. When the radiocarbon ages that control the timing of the Populus subzone are calibrated, the contemporaneous decrease in ice volume and increase in summer insolation are implicated as the ultimate controls of the occurrence of the subzone. (C) 1995 University of Washington.
BibTeX: @article{Bartlein1995, author = {Bartlein, PJ and Edwards, ME and Shafer, SL and Barker, ED}, title = {Calibration of radiocarbon ages and the interpretation of paleoenvironmental records}, journal = {Quaternary Research}, year = {1995}, volume = {44}, number = {3}, pages = {417--424} }
Bartlein2004	Bartlein, P. & Hostetler, S. Gillespie, A.; Porter, S. & Atwater, B. (Hrsg.)	Modeling paleoclimates ( The Quaternary Period in the United States ) [BibTeX] [PDF]	2004	The Quaternary Period in the United States , pp. 563-582	inbook
BibTeX: @inbook{Bartlein2004, author = {Bartlein, PJ and Hostetler, SW}, title = {The Quaternary Period in the United States}, publisher = {Elsevier, Amsterdam}, year = {2004}, pages = {563-582} }
Bartlein2008	Bartlein, P.; Hostetler, S.; Shafer, S.; Holman, J. & Solomon, A.	Temporal and spatial structure in a daily wildfire-start data set from the western United States (1986-96) [Abstract] [BibTeX]	2008	International Journal of Wildland Fire Vol. 17 (1) , pp. 8-17	article
Abstract: The temporal and spatial structure of 332 404 daily fire-start records from the western United States for the period 1986 through 1996 is illustrated using several complimentary visualisation techniques. We supplement maps and time series plots with Hovmoller diagrams that reduce the spatial dimensionality of the daily data in order to reveal the underlying space-time structure. The mapped distributions of all lightning- and human-started fires during the 11-year interval show similar first-order patterns that reflect the broad-scale distribution of vegetation across the West and the annual cycle of climate. Lightning-started fires are concentrated in the summer half-year and occur in widespread outbreaks that last a few days and reflect coherent weather-related controls. In contrast, fires started by humans occur throughout the year and tend to be concentrated in regions surrounding large-population centres or intensive-agricultural areas. Although the primary controls of human-started fires are their location relative to burnable fuel and the level of human activity, spatially coherent, weather-related variations in their incidence can also be noted.
BibTeX: @article{Bartlein2008, author = {Bartlein, PJ and Hostetler, SW and Shafer, SL and Holman, JO and Solomon, AM}, title = {Temporal and spatial structure in a daily wildfire-start data set from the western United States (1986-96)}, journal = {International Journal of Wildland Fire}, year = {2008}, volume = {17}, number = {1}, pages = {8--17} }
Bartlein2003	Bartlein, P.; Hostetler, S.; Shafer, S.; Holman, J. & Solomon, A.	The seasonal cycle of wildfire and climate in the western United States [BibTeX] [PDF]	2003	5th Symposium on Fire and Forest Meteorology, American Meteorological Society , pp. P3.9-1 - P3.9-6	inproceedings
BibTeX: @inproceedings{Bartlein2003, author = {Bartlein, PJ and Hostetler, SW and Shafer, SL and Holman, JO and Solomon, AM}, title = {The seasonal cycle of wildfire and climate in the western United States}, booktitle = {5th Symposium on Fire and Forest Meteorology, American Meteorological Society}, year = {2003}, pages = {P3.9-1 - P3.9-6} }
Bartlein1989	Bartlein, P. & Prentice, I.	Orbital variations, climate and paleoecology [BibTeX]	1989	Trends in Ecology & Evolution Vol. 4 (7) , pp. 195-199	article
BibTeX: @article{Bartlein1989, author = {Bartlein, PJ and Prentice, IC}, title = {Orbital variations, climate and paleoecology}, journal = {Trends in Ecology & Evolution}, year = {1989}, volume = {4}, number = {7}, pages = {195--199} }
Bartlein1986	Bartlein, P.; Prentice, I. & Webb, T.	Climatic response surfaces from pollen data for some eastern North American taxa [BibTeX] [PDF]	1986	Journal of Biogeography Vol. 13 (1) , pp. 35-57	article	vegetation and climate and pollen
BibTeX: @article{Bartlein1986, author = {Bartlein, PJ and Prentice, IC and Webb, T}, title = {Climatic response surfaces from pollen data for some eastern North American taxa}, journal = {Journal of Biogeography}, year = {1986}, volume = {13}, number = {1}, pages = {35--57} }
Bartlein1984	Bartlein, P.; Webb, T. & Fleri, E.	Holocene climatic-change in the northern midwest - pollen-derived estimates [BibTeX]	1984	Quaternary Research Vol. 22 (3) , pp. 361-374	article
BibTeX: @article{Bartlein1984, author = {Bartlein, PJ and Webb, T and Fleri, E}, title = {Holocene climatic-change in the northern midwest - pollen-derived estimates}, journal = {Quaternary Research}, year = {1984}, volume = {22}, number = {3}, pages = {361--374} }
Bartlein1997	Bartlein, P.; Whitlock, C. & Shafter, S.	Future climate in the Yellowstone National Park region and its potential impact on vegetation [Abstract] [BibTeX] [PDF]	1997	Conservation Biology Vol. 11 (3) , pp. 782-792	article	future vegetation change
Abstract: Biotic responses to future changes in global climate are difficult to project for a particular region because the responses involve processes that operate at many spatial scales. This difficulty is exacerbated in mountainous regions, where future vegetation changes are often portrayed as simple upward displacements of vegetation zones in response to warming. We examine the scope of future responses that may occur in a mountainous area by illustrating the potential distributions of selected tree taxa in the region of Yellowstone National Park. The output of a coarse-resolution climate model that incorporated a doubling of carbon dioxide concentration in the atmosphere was interpolated onto a 5-minute grid of topographically adjusted climate data. The output was also used as input into statistical relationships between the occurrence of individual taxa and climate. The simulated vegetation changes include a combination of elevational and directional range adjustments. The range of high-elevation species decreases, and some species become regionally extirpated. The new communities have no analogue in the present-day vegetation because they mix low-elevation montane species currently in the region with extralocal species from the northern and central Rocky Mountains and Pacific Northwest. The projected climate changes within the Yellowstone region and the individualism displayed by species in their potential range adjustments are equal or greater than the changes seen in the paleoecologic record during previous warming intervals. Although the results support conservation strategies that include habitat connectivity, the magnitude of the changes may exceed the ability of species to adjust their ranges. The predicted patterns call into question the adequacy of current management objectives to cope with the scope of future changes.
BibTeX: @article{Bartlein1997, author = {Bartlein, PJ and Whitlock, C and Shafter, SL}, title = {Future climate in the Yellowstone National Park region and its potential impact on vegetation}, journal = {Conservation Biology}, year = {1997}, volume = {11}, number = {3}, pages = {782--792} }
Beckage2008	Beckage, B.; Osborne, B.; Gavin, D.; Pucko, C.; Siccama, T. & Perkins, T.	A rapid upward shift of a forest ecotone during 40 years of warming in the Green Mountains of Vermont [Abstract] [BibTeX] [PDF]	2008	Proceedings of the National Academy of Sciences of the USA Vol. 105 (11) , pp. 4197-4202	article
Abstract: Detecting latitudinal range shifts of forest trees in response to recent climate change is difficult because of slow demographic rates and limited dispersal but may be facilitated by spatially compressed climatic zones along elevation gradients in montane environments. We resurveyed forest plots established in 1964 along elevation transects in the Green Mountains (Vermont) to examine whether a shift had occurred in the location of the northern hardwood-boreal forest ecotone (NBE) from 1964 to 2004. We found a 19% increase in dominance of northern hard-woods from 70% in 1964 to 89% in 2004 in the lower half of the NBE. This shift was driven by a decrease (up to 76%) in boreal and increase (up to 16%) in northern hardwood basal area within the lower portions of the ecotone. We used aerial photographs and satellite imagery to estimate a 91- to 119-m upslope shift in the upper limits of the NBE from 1962 to 2005. The upward shift is consistent with regional climatic change during the same period; interpolating climate data to the NBE showed a 1.1 degrees C increase in annual temperature, which would predict a 208-m upslope movement of the ecotone, along with a 34% increase in precipitation. The rapid upward movement of the NBE indicates. little inertia to climatically induced range shifts in montane forests; the upslope shift may have been accelerated by high turnover in canopy trees that provided opportunities for ingrowth of lower elevation species. Our results indicate that high-elevation forests may be jeopardized by climate change sooner than anticipated.
BibTeX: @article{Beckage2008, author = {Beckage, B and Osborne, B and Gavin, DG and Pucko, C and Siccama, T and Perkins, T}, title = {A rapid upward shift of a forest ecotone during 40 years of warming in the Green Mountains of Vermont}, journal = {Proceedings of the National Academy of Sciences of the USA}, year = {2008}, volume = {105}, number = {11}, pages = {4197--4202} }
Bigelow2003	Bigelow, N.; Brubaker, L.; Edwards, M.; Harrison, S.; Prentice, I.; Anderson, P.; Andreev, A.; Bartlein, P.; Christensen, T.; Cramer, W.; Kaplan, J.; Lozhkin, A.; Matveyeva, N.; Murray, D.; McGuire, A.; Razzhivin, V.; Ritchie, J.; Smith, B.; Walker, D.; Gajewski, K.; Wolf, V.; Holmqvist, B.; Igarashi, Y.; Kremenetskii, K.; Paus, A.; Pisaric, M. & Volkova, V.	Climate change and Arctic ecosystems: 1. Vegetation changes north of 55 degrees N between the last glacial maximum, mid-Holocene, and present [Abstract] [BibTeX] [PDF]	2003	Journal of Geophysical Research-Atmospheres Vol. 108 (D19) , pp. -	article	vegetation and climate
Abstract: [1] A unified scheme to assign pollen samples to vegetation types was used to reconstruct vegetation patterns north of 55degreesN at the last glacial maximum (LGM) and mid-Holocene (6000 years B. P.). The pollen data set assembled for this purpose represents a comprehensive compilation based on the work of many projects and research groups. Five tundra types (cushion forb tundra, graminoid and forb tundra, prostrate dwarf-shrub tundra, erect dwarf-shrub tundra, and low- and high-shrub tundra) were distinguished and mapped on the basis of modern pollen surface samples. The tundra-forest boundary and the distributions of boreal and temperate forest types today were realistically reconstructed. During the mid-Holocene the tundra-forest boundary was north of its present position in some regions, but the pattern of this shift was strongly asymmetrical around the pole, with the largest northward shift in central Siberia (similar to200 km), little change in Beringia, and a southward shift in Keewatin and Labrador (similar to200 km). Low- and high-shrub tundra extended farther north than today. At the LGM, forests were absent from high latitudes. Graminoid and forb tundra abutted on temperate steppe in northwestern Eurasia while prostrate dwarf-shrub, erect dwarf-shrub, and graminoid and forb tundra formed a mosaic in Beringia. Graminoid and forb tundra is restricted today and does not form a large continuous biome, but the pollen data show that it was far more extensive at the LGM, while low- and high-shrub tundra were greatly reduced, illustrating the potential for climate change to dramatically alter the relative areas occupied by different vegetation types.
BibTeX: @article{Bigelow2003, author = {Bigelow, NH and Brubaker, LB and Edwards, ME and Harrison, SP and Prentice, IC and Anderson, PM and Andreev, AA and Bartlein, PJ and Christensen, TR and Cramer, W and Kaplan, JO and Lozhkin, AV and Matveyeva, NV and Murray, DF and McGuire, AD and Razzhivin, VY and Ritchie, JC and Smith, B and Walker, DA and Gajewski, K and Wolf, V and Holmqvist, BH and Igarashi, Y and Kremenetskii, K and Paus, A and Pisaric, MFJ and Volkova, VS}, title = {Climate change and Arctic ecosystems: 1. Vegetation changes north of 55 degrees N between the last glacial maximum, mid-Holocene, and present}, journal = {Journal of Geophysical Research-Atmospheres}, year = {2003}, volume = {108}, number = {D19}, pages = {--} }
Bigler2007	Bigler, C.; Gavin, D.; Gunning, C. & Veblen, T.	Drought induces lagged tree mortality in a subalpine forest in the Rocky Mountains [Abstract] [BibTeX] [PDF]	2007	Oikos Vol. 116 (12) , pp. 1983-1994	article
Abstract: Extreme climatic events are key factors in initiating gradual or sudden changes in forest ecosystems through the promotion of severe, tree-killing disturbances such as fire, blowdown, and widespread insect outbreaks. In contrast to these climatically-incited disturbances, little is known about the more direct effect of drought on tree mortality, especially in high-elevation forests. Therefore projections of drought-induced mortality under future climatic conditions remain uncertain. For a subalpine forest landscape in the Rocky Mountains of northern Colorado (USA), we quantified lag effects of drought on mortality of Engelmann spruce Picea engelmannii, subalpine fir Abies lasiocarpa, and lodgepole pine Pinus contorta. For the period 1910-2004, we related death dates of 164 crossdated dead trees to early-season and late-season droughts. Following early-season droughts, spruce mortality increased over five years and fir mortality increased sharply over 11 years. Following late-season droughts, spruce showed a small increase in mortality within one year, whereas fir showed a consistent period of increased mortality over two years. Pine mortality was not affected by drought. Low pre-drought radial growth rates predisposed spruce and fir to drought-related mortality. Spruce and fir trees that died during a recent drought (2000-2004) had significantly lower pre-drought growth rates than live neighbour trees. Overall, we found large interspecific differences in drought-related mortality with fir showing the strongest effect followed by spruce and pine. This direct influence of climatic variability on differential tree mortality has the potential for driving large-scale changes in subalpine forests of the Rocky Mountains.
BibTeX: @article{Bigler2007, author = {Bigler, C and Gavin, DG and Gunning, C and Veblen, TT}, title = {Drought induces lagged tree mortality in a subalpine forest in the Rocky Mountains}, journal = {Oikos}, year = {2007}, volume = {116}, number = {12}, pages = {1983--1994} }
Birkeland1996	Birkeland, K. & Mock, C.	Atmospheric Circulation Patterns Associated with Heavy Snowfall Events, Bridger Bowl, Montana, U.S.A. [BibTeX] [Figures]	1996	Mountain Research and Development Vol. 16 , pp. 281-286	article	synoptic climatology
BibTeX: @article{Birkeland1996, author = {Birkeland, KW and Mock, CJ}, title = {Atmospheric Circulation Patterns Associated with Heavy Snowfall Events, Bridger Bowl, Montana, U.S.A.}, journal = {Mountain Research and Development}, year = {1996}, volume = {16}, pages = {281-286}, note = {http://geography.uoregon.edu/envchange/figures/Mock-and-Birkeland-MRD-1996-figs/mtsnow.htm} }
Blanton2009	Blanton, P. & Marcus, W.	Railroads, roads and lateral disconnection in the river landscapes of the continental United States [Abstract] [BibTeX] [PDF]	2009	Geomorphology Vol. 112 (3-4) , pp. 212-227	article	fluvial geomorphology
Abstract: Railroads and roads are ubiquitous features in the river corridors of the United States. However, their impact on hydrologic, geomorphic, and ecological processes in fluvial and riparian landscapes has not been systematically explored at regional or continental extents. This study documents the geographic distribution of roads and railroads in the alluvial floodplains of the continental United States and the regional variability of their potential impacts on lateral connectivity and resultant channel and floodplain structure and function. We use national scale data sets and GIS analysis to derive data on stream-transportation network interactions in two broad categories: (1) crossing impacts, such as bridges and culverts, and (2) impacts where transportation infrastructure acts as a longitudinal dam along the stream channel, causing lateral floodplain disconnection. Potential stream crossing impacts are greatest in regions with long histories of road and railroad development and relatively low relief, such as the Mid-Atlantic, New England, and the Lower Mississippi and Ohio Valleys. Potential lateral disconnections are more prevalent in rugged regions such as the Western US. and Appalachians where transportation routes follow river corridors along valley bottoms. Based on these results, we develop a conceptual model that suggests that the area of lateral disconnection due to transportation infrastructure should be most extensive in mid-sized alluvial valleys in relatively rugged settings. The result of this disconnection is the disruption of the long-term, cut-and-fill alluviation and of the shorter-term flood and flow pulse processes that create and maintain ecosystem function in river landscapes. The tremendous extent of transportation infrastructure in alluvial valleys documented in this study suggests a revision to H.B.N. Hynes' statement that the valley rules the stream. Instead, it appears that in modem landscapes of the U.S. the valley rules the transportation network - and the transportation network rules the stream. (C) 2009 Elsevier B.V. All fights reserved.
BibTeX: @article{Blanton2009, author = {Blanton, P and Marcus, WA}, title = {Railroads, roads and lateral disconnection in the river landscapes of the continental United States}, journal = {Geomorphology}, year = {2009}, volume = {112}, number = {3-4}, pages = {212--227} }
Bonfils2004	Bonfils, C.; de Noblet-Ducoudre, N.; Guiot, J. & Bartlein, P.	Some mechanisms of mid-Holocene climate change in Europe, inferred from comparing PMIP models to data [Abstract] [BibTeX] [PDF]	2004	Climate Dynamics Vol. 23 (1) , pp. 79-98	article	paleoclimatic analysis and data-model comparisons
Abstract: We propose a new approach for comparing mid-Holocene climates from 18 PMIP simulations with climate reconstructions of winter and growing season temperatures and the annual water budget inferred from European pollen and lake-level data. A cluster analysis is used to extract patterns of multivariate climate response from the reconstructions; these are then compared to the patterns simulated by models. According to paleodata, summers during mid-Holocene were warmer-than-present in the north, and cooler-than-present in the south, while winters were colder-than-present in the southwest but milder-than-present in the northeast. Whereas warmer summers and colder winters may easily be explained as a direct response to the amplified seasonal cycle of insolation during the mid-Holocene, the other recorded responses are less straightforward to explain. We have identified, from the models that correctly simulate the recorded climate change, two important atmospheric and hydrological processes that can compensate for direct insolation effects. First, a stronger-than-present airflow from southwestern Europe that veers to the north over Eastern Europe, in winter, can consistently explain the reconstructed changes in this season's temperatures and water budget. Second, the increased winter soil moisture allows a shift of the partitioning of net radiative energy towards latent rather than sensible heat fluxes, thereby decreasing surface temperature during the following summer season. Our approach therefore solves one of the recurring problems in model-data comparisons that arises when a model simulates the correct response but in the wrong location (as a consequence, for instance, of model resolution and topography).
BibTeX: @article{Bonfils2004, author = {Bonfils, C and de Noblet-Ducoudre, N and Guiot, J and Bartlein, P}, title = {Some mechanisms of mid-Holocene climate change in Europe, inferred from comparing PMIP models to data}, journal = {Climate Dynamics}, year = {2004}, volume = {23}, number = {1}, pages = {79--98} }
Briles2005	Briles, C.; Whitlock, C. & Bartlein, P.	Postglacial vegetation, fire, and climate history of the Siskiyou Mountains, Oregon, USA [Abstract] [BibTeX] [PDF]	2005	Quaternary Research Vol. 64 (1) , pp. 44-56	article	fire: modern and paleo
Abstract: The forests of the Siskiyou Mountains are among the most diverse in North America, yet the long-term relationship among climate, diversity, and natural disturbance is not well known. Pollen, plant macrofossils, and high-resolution charcoal data from Bolan Lake, Oregon, were analyzed to reconstruct a 17,000-yr-long environmental history of high-elevation forests in the region. In the late-glacial period, the presence of a subalpine parkland of Artemisia, Poaceae, Pinus, and Tsuga with infrequent fires suggests cool dry conditions. After 14,500 cal yr B.P., a closed forest of Abies, Pseudotsuga, Tsuga, and Alnus rubra with more frequent fires developed which indicates more mesic conditions than before. An open woodland of Pinus, Quercus, and Cupressaceae, with higher fire activity than before, characterized the early Holocene and implies warmer and drier conditions than at present. In the late Holocene, Abies and Picea were more prevalent in the forest, suggesting a return to cool wet conditions, although fire-episode frequency remained relatively high. The modem forest of Abies and Pseudotsuga and the present-day fire regime developed ca. 2100 cal yr B.P. and indicates that conditions had become slightly drier than before. Sub-millennial-scale fluctuations in vegetation and fire activity suggest climatic variations during the Younger Dryas interval and within the early Holocene period. The timing of vegetation changes in the Bolan Lake record is similar to that of other sites in the Pacific Northwest and Klamath region, and indicates that local vegetation communities were responding to regional-scale climate changes. The record implies that climate-driven millennial- to centennial-scale vegetation and fire change should be considered when explaining the high floristic diversity observed at present in the Siskiyou Mountains. (c) 2005 University of Washington. All rights reserved.
BibTeX: @article{Briles2005, author = {Briles, CE and Whitlock, C and Bartlein, PJ}, title = {Postglacial vegetation, fire, and climate history of the Siskiyou Mountains, Oregon, USA}, journal = {Quaternary Research}, year = {2005}, volume = {64}, number = {1}, pages = {44--56} }
Briles2008	Briles, C.; Whitlock, C.; Bartlein, P. & Higuera, P.	Regional and local controls on postglacial vegetation and fire in the Siskiyou Mountains, northern California, USA [Abstract] [BibTeX] [PDF]	2008	Palaeogeography Palaeoclimatology Palaeoecology Vol. 265 (1-2) , pp. 159-169	article	fire: modern and paleo
Abstract: The Siskiyou Mountains of northwestern California and southwestern Oregon are a floristic hotspot, and the high diversity of conifers there likely results from a combination of geological, ecological, climatological and historical factors. To evaluate how past climate variability has influenced the composition, structure and fire regime of the Siskiyou forests, pollen, charcoal, and lithological evidence was examined from two lakes along a moisture gradient to reconstruct the vegetation, fire and climate history. The late-glacial/Early Holocene transition period, subalpine parkland was replaced by a closed forest of Pinus, Cupressaceae, Abies and Pseudotsuga and more frequent fires a 1000 years earlier at the wetter site, and it is likely that reduced Pacific Ocean upwelling created warmer drier conditions at the coast. In the Early Holocene, Pinus, Cupressaceae were less abundant and fire less frequent at the coastal site during a period of increased coastal upwelling and fog production. In the Late Holocene, Abies, Pseudotsuga, Pinus, and Quercus vaccinifolia increased in the forest at both sites suggesting a widespread response to cooling. Fewer fires at the wetter site may account for the abundance of Picea breweriana within the last 1000 years. The comparison of the two records implies that large-scale controls in climate during the last 14,000 cal yr BP have resulted in major changes in vegetation and fire regime. Asynchrony in the ecosystem response of wetter and drier sites arises from small-scale spatial variations in effective moisture and temperature resulting from topographically-influenced microclimates and coastal-to-inland climate gradients. (C) 2008 Elsevier B.V. All rights reserved.
BibTeX: @article{Briles2008, author = {Briles, CE and Whitlock, C and Bartlein, PJ and Higuera, P}, title = {Regional and local controls on postglacial vegetation and fire in the Siskiyou Mountains, northern California, USA}, journal = {Palaeogeography Palaeoclimatology Palaeoecology}, year = {2008}, volume = {265}, number = {1-2}, pages = {159--169} }
Brunelle2005	Brunelle, A.; Whitlock, C.; Bartlein, P. & Kipfmueller, K.	Holocene fire and vegetation along environmental gradients in the Northern Rocky Mountains [Abstract] [BibTeX] [PDF]	2005	Quaternary Science Reviews Vol. 24 (20-21) , pp. 2281-2300	article	fire: modern and paleo
Abstract: Holocene records of fire, vegetation, and climate were reconstructed from four sites in the Bitterroot Range region of the Northern Rocky Mountains in order to examine the vegetation and fire histories and evaluate the hypothesis proposed by Whitlock and Bartlein (1993) regarding the effects of increased summer insolation on precipitation patterns. Vegetation history in the series of sites was broadly similar. In the late-glacial period, the pollen data suggest open parkland dominated by Picea or alpine meadow, which reflect conditions cooler and drier than present. These open forests were replaced in the early to middle Holocene by forests composed mainly of Pinus and Pseudotsuga, which suggest conditions warmer than present. Modern forest compositions were in place by ca 3000 cal yr BP, and small variations in the timing of the vegetation shifts reflect local differences among sites. The long-term trends in fire occurrence support the hypothesis proposed by Whitlock and Bartlein (1993) that precipitation regimes were sharpened during the early Holocene summer insolation maximum but their location has remained unchanged as a result of topographic constraints. Sites located in areas currently summer-dry were drier-than-present during the early Holocene and fires were more frequent. Conversely, sites located in the areas that are summer-wet at present were wetter-than-present in the early Holocene, and fires were less frequent. On millennial time scales it appears that the climate boundary is controlled by topography and does not shift. (c) 2005 Elsevier Ltd. All rights reserved.
BibTeX: @article{Brunelle2005, author = {Brunelle, A and Whitlock, C and Bartlein, P and Kipfmueller, K}, title = {Holocene fire and vegetation along environmental gradients in the Northern Rocky Mountains}, journal = {Quaternary Science Reviews}, year = {2005}, volume = {24}, number = {20-21}, pages = {2281--2300} }
Chase2008	Chase, M.; Bleskie, C.; Walker, I.; Gavin, D. & Hu, F.	Midge-inferred Holocene summer temperatures in Southeastern British Columbia, Canada [Abstract] [BibTeX] [PDF]	2008	Palaeogeography Palaeoclimatology Palaeoecology Vol. 257 (1-2) , pp. 244-259	article
Abstract: Using fossil midge stratigraphies, we inferred Holocene summer temperatures at three subalpine lakes in eastern British Columbia. The late-glacial sediment indicated cool conditions, with an abundance of Microspectra atrofasciata/radialis type fossils at Thunder Lake and Redmountain Lake, and Sergentia at Windy Lake. Sergentia and Tanytarsus lugens/Corynocera oliveri type were dominant in the early Holocene, together with Chironomus at Redmountain Lake. At Thunder and Windy lakes, the early Holocene was dominated by warm-adapted taxa such as Microtendipes. Quantitative midge-temperature inference models reconstruct a 4 to 8 degrees C rise in mean July air temperature for Windy and Thunder lakes at the Pleistocene/Holocene transition. Early-Holocene temperatures averaged 3 to 4 degrees C warmer than those extant today. In contrast, no long-term temperature trend was evident at Redmountain Lake. This site may not reflect actual trends in air temperature due to runoff from a persistent snow pack in the watershed. Comparison of midge and pollen data suggests an inverse relationship between summer temperature and precipitation through the middle to late Holocene. (C) 2007 Elsevier B.V. All rights reserved.
BibTeX: @article{Chase2008, author = {Chase, M and Bleskie, C and Walker, IR and Gavin, DG and Hu, FS}, title = {Midge-inferred Holocene summer temperatures in Southeastern British Columbia, Canada}, journal = {Palaeogeography Palaeoclimatology Palaeoecology}, year = {2008}, volume = {257}, number = {1-2}, pages = {244--259} }
Clark1995	Clark, P. & Bartlein, P.	Correlation of late Pleistocene glaciation in the western United States with North Atlantic Heinrich events [Abstract] [BibTeX]	1995	Geology Vol. 23 (6) , pp. 483-486	article
Abstract: A survey of the chronology of late Pleistocene glaciers in the western United States indicates a record of glacier advances during the last glaciation which is more variable than that predicted by orbital forcing. Numerical dating of late Pleistocene deposits from the Puget lobe of the Cordilleran ice sheet and alpine glaciers and ice caps in the Rocky Mountains and Cascade Range suggests that advances and retreats of these glaciers were in phase with episodes of growth and collapse of the Laurentide ice sheet associated with the North Atlantic Heinrich events. Specifically, the existing chronologies indicate that these glaciers were advancing to their terminal areas up to several thousand years before a Heinrich event and retreated shortly thereafter, Because midlatitude glaciers respond relatively rapidly to climate change, this complex record of glacial fluctuations suggests mechanisms of climate forcing in western North America that are in some way tied to Heinrich events, One possible mechanism involves southerly and northerly displacement of the jet stream across the western United States in response to growth and collapse of the Laurentide ice sheet.
BibTeX: @article{Clark1995, author = {Clark, PU and Bartlein, PJ}, title = {Correlation of late Pleistocene glaciation in the western United States with North Atlantic Heinrich events}, journal = {Geology}, year = {1995}, volume = {23}, number = {6}, pages = {483--486} }
Clegg2005	Clegg, B.; Tinner, W.; Gavin, D. & Hu, F.	Morphological differentiation of Betula (birch) pollen in northwest North America and its palaeoecological application [Abstract] [BibTeX] [PDF]	2005	Holocene Vol. 15 (2) , pp. 229-237	article
Abstract: Lake sediments from arcto-boreal regions commonly contain abundant Betula pollen. However, palaeoenvironmental interpretations of Betula pollen are often ambiguous because of the lack of reliable morphological features to distinguish among ecologically distinct Betula species in western North America. We measured the grain diameters and pore depths of pollen from three tree-birch species (B. papyrifera, B. kenaica and B. neoalaskana) and two shrub-birch species (B. glandulosa and B. nana), and calculated the ratio of grain diameter to pore depth (D/P ratio). No statistical difference exists in all three parameters between the shrub-birch species or between two of the tree-birch species (B. kenaica and B. papyrifera), and B. neoalaskana is intermediate between the shrub-birch and the other two tree-birch species. However, mean pore depth is significantly larger for the tree species than for the shrub species. In contrast, mean grain diameter cannot distinguish tree and shrub species. Mean D/P ratio separates tree and shrub species less clearly than pore depth, but this ratio can be used for verification. The threshold for distinguishing pollen of tree versus shrub birch lies at 2.55 mm and 8.30 for pore depth and D/P ratio, respectively. We applied these thresholds to the analysis of Betula pollen in an Alaskan lake-sediment core spanning the past 800 years. Results show that shrub birch increased markedly at the expense of tree birch during the 'Little Ice Age'; this pattern is not discernible in the profile of total birch pollen.
BibTeX: @article{Clegg2005, author = {Clegg, BF and Tinner, W and Gavin, DG and Hu, FS}, title = {Morphological differentiation of Betula (birch) pollen in northwest North America and its palaeoecological application}, journal = {Holocene}, year = {2005}, volume = {15}, number = {2}, pages = {229--237} }
Colombaroli2010	Colombaroli, D. & Gavin, D.	Highly episodic fire and erosion regime over the past 2,000 y in the Siskiyou Mountains, Oregon [Abstract] [BibTeX] [PDF]	2010	Proceedings of the National Academy of Sciences of the USA Vol. 107 (44) , pp. 18909-18914	article
Abstract: Fire is a primary mode of natural disturbance in the forests of the Pacific Northwest. Increased fuel loads following fire suppression and the occurrence of several large and severe fires have led to the perception that in many areas there is a greatly increased risk of high-severity fire compared with presettlement forests. To reconstruct the variability of the fire regime in the Siskiyou Mountains, Oregon, we analyzed a 10-m, 2,000-y sediment core for charcoal, pollen, and sedimentological data. The record reveals a highly episodic pattern of fire in which 77% of the 68 charcoal peaks before Euro-American settlement cluster within nine distinct periods marked by a 15-y mean interval. The 11 largest charcoal peaks are significantly related to decadal-scale drought periods and are followed by pulses of minerogenic sediment suggestive of rapid sediment delivery. After logging in the 1950s, sediment load was increased fourfold compared with that from the most severe presettlement fire. Less severe fires, marked by smaller charcoal peaks and no sediment pulses, are not correlated significantly with drought periods. Pollen indicators of closed forests are consistent with fire-free periods of sufficient length to maintain dense forest and indicate a fire-triggered switch to more open conditions during the Medieval Climatic Anomaly. Our results indicate that over millennia fire was more episodic than revealed by nearby shorter tree-ring records and that recent severe fires have precedents during earlier drought episodes but also that sediment loads resulting from logging and road building have no precedent in earlier fire events.
BibTeX: @article{Colombaroli2010, author = {Colombaroli, D and Gavin, DG}, title = {Highly episodic fire and erosion regime over the past 2,000 y in the Siskiyou Mountains, Oregon}, journal = {Proceedings of the National Academy of Sciences of the USA}, year = {2010}, volume = {107}, number = {44}, pages = {18909--18914} }
Daniau2010	Daniau, A.; Harrison, S. & Bartlein, P.	Fire regimes during the Last Glacial [Abstract] [BibTeX]	2010	Quaternary Science Reviews Vol. 29 (21-22) , pp. 2918-2930	article
Abstract: Sedimentary charcoal records document changes in fire regime. We have identified 67 sites (30 sites with better than millennial resolution) which have records for some part of the Last Glacial to analyse changes in global fire regimes. Fire was consistently lower during the glacial than during the Eemian and Holocene. Within the glacial, Marine Isotope Stage (MIS) 3 is characterised globally by more fire than MIS 2. The signal for MIS 4 is less clear: there is more fire in the Northern Hemisphere and less fire in the Southern Hemisphere than during MIS 2 and 3. The records, most particularly records from the northern extratropics, show millennial-scale variability in fire regimes corresponding to the rapid climate changes associated with Dansgaard-Oeschger (D-O) cycles. Most of the D-O cycles during the Last Glacial and all of the Heinrich stadials are apparent in the composite global record of fire regime: fire increases during D-O warming events and decreases during intervals of rapid cooling. Our analyses show that fire regimes show a lagged response to rapid climate changes of ca 100-200 years in the case of D-O warming events, ca 0-100 years in the case of D-O cooling events and ca 200 years in the case of Heinrich Stadials. The Strong climatic variability experienced during the glacial resulted in important changes in fire regimes even though the base level of biomass burning was less than today. (C) 2009 Elsevier Ltd. All rights reserved.
BibTeX: @article{Daniau2010, author = {Daniau, AL and Harrison, SP and Bartlein, PJ}, title = {Fire regimes during the Last Glacial}, journal = {Quaternary Science Reviews}, year = {2010}, volume = {29}, number = {21-22}, pages = {2918--2930} }
Deligne2010	Deligne, N.; Cashman, K.; Gavin, D. & Roering, J.	Reforestation of Collier Cone lava flow, central Oregon Cascades [BibTeX]	2010	Geochimica et Cosmochimica Acta Vol. 74 (12) , pp. A221-A221-A221-A221	conference
BibTeX: @conference{Deligne2010, author = {Deligne, NI and Cashman, KV and Gavin, DG and Roering, JJ}, title = {Reforestation of Collier Cone lava flow, central Oregon Cascades}, journal = {Geochimica et Cosmochimica Acta}, year = {2010}, volume = {74}, number = {12}, pages = {A221-A221--A221-A221} }
Diffenbaugh2006	Diffenbaugh, N.; Ashfaq, M.; Shuman, B.; Williams, J. & Bartlein, P.	Summer aridity in the United States: Response to mid-Holocene changes in insolation and sea surface temperature [Abstract] [BibTeX] [PDF]	2006	Geophysical Research Letters Vol. 33 (22) , pp. -	article
Abstract: We examine the response of summer precipitation to mid-Holocene insolation forcing and insolation-induced changes in sea surface temperature. Using a high-resolution nested climate modeling system, we find that mid-Holocene insolation forcing results in drier-than-present conditions over the central continental United States ( U. S.) and northern Rocky Mountains, as well as wetter-than-present conditions over the Atlantic seaboard and northwestern Great Plains. We find that changes in summer precipitation are dominated by changes in large-scale processes, with similar patterns of change in the global and nested models. We also find that insolation-induced changes in sea surface temperature do not change the basic pattern of precipitation response, primarily because the dynamical response is very similar with and without sea surface temperature changes. Notably, drier-than-present conditions over the central U. S. are associated with enhanced anticyclonic circulation aloft over the mid-continent and reduced low-level moisture content over the Gulf of Mexico and south-central U. S., while wetter-than-present conditions over the Atlantic seaboard are associated with enhanced low-level cyclonic circulation and elevated low-level moisture content. The simulated patterns of precipitation and soil moisture agree with proxy moisture records from most regions, indicating both that insolation was the strongest determinant of mid-Holocene summer aridity in the continental U. S. and that high-resolution nested climate modeling systems are able to capture the basic response of midlatitude warm-season aridity to changes in external climate forcing.
BibTeX: @article{Diffenbaugh2006, author = {Diffenbaugh, NS and Ashfaq, M and Shuman, B and Williams, JW and Bartlein, PJ}, title = {Summer aridity in the United States: Response to mid-Holocene changes in insolation and sea surface temperature}, journal = {Geophysical Research Letters}, year = {2006}, volume = {33}, number = {22}, pages = {--} }
Diffenbaugh2003	Diffenbaugh, N.; Sloan, L.; Snyder, M.; Bell, J.; Kaplan, J.; Shafer, S. & Bartlein, P.	Vegetation sensitivity to global anthropogenic carbon dioxide emissions in a topographically complex region [Abstract] [BibTeX] [PDF]	2003	Global Biogeochemical Cycles Vol. 17 (2) , pp. -	article	future vegetation changes
Abstract: [1] Anthropogenic increases in atmospheric carbon dioxide (CO2) concentrations may affect vegetation distribution both directly through changes in photosynthesis and water-use efficiency, and indirectly through CO2-induced climate change. Using an equilibrium vegetation model (BIOME4) driven by a regional climate model (RegCM2.5), we tested the sensitivity of vegetation in the western United States, a topographically complex region, to the direct, indirect, and combined effects of doubled preindustrial atmospheric CO2 concentrations. Those sensitivities were quantified using the kappa statistic. Simulated vegetation in the western United States was sensitive to changes in atmospheric CO2 concentrations, with woody biome types replacing less woody types throughout the domain. The simulated vegetation was also sensitive to climatic effects, particularly at high elevations, due to both warming throughout the domain and decreased precipitation in key mountain regions such as the Sierra Nevada of California and the Cascade and Blue Mountains of Oregon. Significantly, when the direct effects of CO2 on vegetation were tested in combination with the indirect effects of CO2-induced climate change, new vegetation patterns were created that were not seen in either of the individual cases. This result indicates that climatic and nonclimatic effects must be considered in tandem when assessing the potential impacts of elevated CO2 levels.
BibTeX: @article{Diffenbaugh2003, author = {Diffenbaugh, NS and Sloan, LC and Snyder, MA and Bell, JL and Kaplan, J and Shafer, SL and Bartlein, PJ}, title = {Vegetation sensitivity to global anthropogenic carbon dioxide emissions in a topographically complex region}, journal = {Global Biogeochemical Cycles}, year = {2003}, volume = {17}, number = {2}, pages = {--} }
Edwards1991	Edwards, M. & McDowell, P.	Interglacial deposits at Birch Creek, northeast interior Alaska [BibTeX]	1991	Quaternary Research Vol. 35 (1) , pp. 41-52	article
BibTeX: @article{Edwards1991, author = {Edwards, ME and McDowell, PF}, title = {Interglacial deposits at Birch Creek, northeast interior Alaska}, journal = {Quaternary Research}, year = {1991}, volume = {35}, number = {1}, pages = {41--52} }
Edwards2001	Edwards, M.; Mock, C.; Finney, B.; Barber, V. & Bartlein, P.	Potential analogues for paleoclimatic variations in eastern interior Alaska during the past 14,000 yr: atmospheric-circulation controls of regional temperature and moisture responses [Abstract] [BibTeX] [Figures] [PDF]	2001	Quaternary Science Reviews Vol. 20 (1-3) , pp. 189-202	article	modern climate analogues
Abstract: The paleoclimatic history of a region can be viewed as a series of surface temperature and moisture anomalies through time. The effects of changes in large-scale climatic controls (e.g., insolation, major circulation controls) can be mediated by the influence of smaller-scale controls (e.g., topographic barriers, coastlines); this may result in heterogenous surface climatic responses at the regional and sub-regional scale. Divergent paleoclimatic trajectories between regions may be explainable in terms of such meso-scale patterns. Using modern analogues for paleoclimate we examine how the sequence of climatic variations in eastern interior Alaska during the interval 12,000-0 C-14 yr BP could have been generated by specific atmospheric circulation patterns. Fossil-pollen and lake-level records document the long-term trends in temperature and effective moisture for the region. Water-balance modelling provides additional estimates of paleoprecipitation. Synoptic climatological patterns are described using the modern (instrumental) record of upper-level and sea-level pressure, surface temperature, and precipitation. At 12,000 C-14 yr BP, eastern interior Alaska was cooler and drier than present, a situation generated today by a southward displacement of the jet stream. Conditions warmer and drier than present at 9000 C-14 yr BP may have been generated by increased ridging north of Alaska and a weakened westerly circulation. Warmer, wetter conditions than present possibly prevailed in the late-middle Holocene; these might reflect ridging over Alaska and troughing further west. Cool, wet conditions feature enhanced westerly flow into Alaska through an eastward shift in the east Asian trough and positive pressure anomalies in the North Pacific; they may be analogous to cold periods of the Little Ice Age. The analogues demonstrate how surface conditions in other parts of Beringia may sometimes be similar to, while at other times different from those in the eastern interior. These broader spatial patterns provide hypotheses about past climates that can be tested with paleoclimatological data. For example, the widespread positive temperature anomalies associated with the warm/dry (9000 C-14 yr BP) analogue fit with the expansion northward of the eastern Siberian treeline. The anomalously cool conditions in northeast Siberia associated with the warm/wet analogue may explain the continued (late-middle Holocene) treeline advance in Alaska while there was retreat in Siberia. (C) 2000 Elsevier Science Ltd. All rights reserved.
BibTeX: @article{Edwards2001, author = {Edwards, ME and Mock, CJ and Finney, BP and Barber, VA and Bartlein, PJ}, title = {Potential analogues for paleoclimatic variations in eastern interior Alaska during the past 14,000 yr: atmospheric-circulation controls of regional temperature and moisture responses}, journal = {Quaternary Science Reviews}, year = {2001}, volume = {20}, number = {1-3}, pages = {189--202}, note = {http://geography.uoregon.edu/envchange/figures/Edwards-etal-QSR-2001-figs/index.html} }
Farrera1999	Farrera, I.; Harrison, S.; Prentice, I.; Ramstein, G.; Guiot, J.; Bartlein, P.; Bonnefille, R.; Bush, M.; Cramer, W.; von Grafenstein, U.; Holmgren, K.; Hooghiemstra, H.; Hope, G.; Jolly, D.; Lauritzen, S.; Ono, Y.; Pinot, S.; Stute, M. & Yu, G.	Tropical climates at the Last Glacial Maximum: a new synthesis of terrestrial palaeoclimate data. I. Vegetation, lake levels and geochemistry [Abstract] [BibTeX]	1999	Climate Dynamics Vol. 15 (11) , pp. 823-856	article
Abstract: Palaeodata in synthesis form are needed as benchmarks for the Palaeoclimate Modelling Intercomparison Project (PMIP), Advances since the last synthesis of terrestrial palaeodata from the last glacial maximum (LGM) call for a new evaluation, especially of data from the tropics. Here pollen, plant-macrofossil, lake-level, noble gas (from groundwater) and delta(18)O (from speleothems) data are compiled for 18 +/- 2 ka (C-14), 32 degrees N-33 degrees S. The reliability of the data was evaluated using explicit criteria and some types of data were re-analysed using consistent methods in order to derive a set of mutually consistent palaeoclimate estimates of mean temperature of the coldest month (MTCO), mean annual temperature (MAT), plant available moisture (PAM) and runoff (P-E). Cold-month temperature (MAT) anomalies from plant data range from -1 to -2 K near sea level in Indonesia and the S Pacific, through -6 to -8 K at many high-elevation sites to -8 to -15K in S China and the SE USA. MAT anomalies from groundwater or speleothems seem more uniform (-4 to -6 K), but the data are as yet sparse; a clear divergence between MAT and cold-month estimates from the same region is seen only in the SE USA, where cold-air advection is expected to have enhanced cooling in winter. Regression of all cold-month anomalies against site elevation yielded an estimated average cooling of - 2.5 to - 3 K at modern sea level, increasing to approximate to - 6 K by 3000m. How ever, Neotropical sites showed larger than the average sea-level cooling (- 5 to - 6 K) and a non-significant elevation effect, whereas W and S Pacific sites showed much less sea-level cooling (- 1 K) and a stronger elevation effect. These findings support the inference that tropical sea-surface temperatures (SSTs) were lower than the CLIMAP estimates, but they limit the plausible average tropical sea-surface cooling, and they support the existence of CLIMAP-like geographic patterns in SST anomalies. Trends of PAM and lake levels indicate wet LGM conditions in the W USA, and at the highest elevations, with generally dry conditions elsewhere. These results suggest a colder-than-present ocean surface producing a weaker hydrological cycle, more arid continents, and arguably steeper-than-present terrestrial lapse rates. Such linkages are supported by recent observations on freezing-level height and tropical SSTs, moreover, simulations of "greenhouse" and LGM climates point to several possible feedback processes by which low-level temperature anomalies might be amplified aloft.
BibTeX: @article{Farrera1999, author = {Farrera, I and Harrison, SP and Prentice, IC and Ramstein, G and Guiot, J and Bartlein, PJ and Bonnefille, R and Bush, M and Cramer, W and von Grafenstein, U and Holmgren, K and Hooghiemstra, H and Hope, G and Jolly, D and Lauritzen, SE and Ono, Y and Pinot, S and Stute, M and Yu, G}, title = {Tropical climates at the Last Glacial Maximum: a new synthesis of terrestrial palaeoclimate data. I. Vegetation, lake levels and geochemistry}, journal = {Climate Dynamics}, year = {1999}, volume = {15}, number = {11}, pages = {823--856} }
Foit2004	Foit, F.; Gavin, D. & Hu, F.	The tephra stratigraphy of two lakes in south-central British Columbia, Canada and its implications for mid-late Holocene volcanic activity at Glacier Peak and Mount St. Helens, Washington, USA [Abstract] [BibTeX] [PDF]	2004	Canadian Journal of Earth Sciences Vol. 41 (12) , pp. 1401-1410	article
Abstract: Several mid-late Holocene Glacier Peak tephras along with Mazama and Mount St. Helens Wn and P tephras were found in cores from Cooley and Rockslide lakes in southeastern British Columbia, similar to300 km northeast of Glacier Peak. The sediments in Cooley Lake host the late Holocene Glacier Peak A tephra (2010 calibrated (cal) years BP), four separate Glacier Peak Dusty Creek (GPDC) tephras (5780-5830 cal years BP), and a Glacier Peak set D tephra (6060 cal years BP). This is the first report of Glacier Peak A and D tephras in British Columbia. The A tephra has been correlated on the basis of glass composition and age to a late Holocene Glacier Peak tephra in the sediments of Big Twin Lake, 75 km northeast of Glacier Peak. The glasses in the four GPDC tephra layers from Cooley Lake are compositionally indistinguishable from those in Mount Barr Cirque and Frozen lakes in southwestern British Columbia. The layers likely represent four eruptions taking place over 50 years. Although set D tephra has not been correlated to a known proximal or distal deposit, its glass bears the Glacier Peak glass compositional signature and its interpolated age corresponds to the initiation of the set D eruptive period. The presence of GPDC tephra in lake sediments across southern British Columbia suggests a broad plume trajectory to the north and northeast, whereas the apparent absence of the A and D tephras in all but Cooley Lake suggest plumes with a northeasterly direction.
BibTeX: @article{Foit2004, author = {Foit, FF and Gavin, DG and Hu, FS}, title = {The tephra stratigraphy of two lakes in south-central British Columbia, Canada and its implications for mid-late Holocene volcanic activity at Glacier Peak and Mount St. Helens, Washington, USA}, journal = {Canadian Journal of Earth Sciences}, year = {2004}, volume = {41}, number = {12}, pages = {1401--1410} }
Fonstad2010	Fonstad, M. & Marcus, W.	High resolution, basin extent observations and implications for understanding river form and process [Abstract] [BibTeX]	2010	Earth Surface Processes and Landforms Vol. 35 (6) , pp. 680-698	article	remote sensing fluvial geomorphology
Abstract: Fifty years of fluvial studies have posited a variety of conceptual frameworks for characterizing river forms and processes throughout entire basins, including hydraulic geometry, the river continuum concept, self-organized criticality, and sediment links. This article uses basin-extent, high resolution observations of fluvial forms in the Nueces River basin, Texas, and Yellowstone National Park to evaluate the ability of these frameworks to characterize system behavior across a multitude of scales. The Nueces data were collected with remote sensing methods and the Yellowstone data were collected through extensive field surveys. The data resolution, spatial extent, and quality of these data sets allow direct comparison between the two areas. The 'hyperscale' comparison supports using of each these frameworks at specific scales, but also indicates an irreducible amount of variation in both datasets across many different scales that is not captured by the conceptual frameworks. Moreover, the scales and locations where one framework, such as hydraulic geometry, works well are often not the same scales and locations where another framework, such as the river continuum concept, works well. Because the conceptual frameworks appear to operate at scales and locations distinct from one another, the measurement approaches necessary to observe them must also be at different scales and locations. For example, 'seeing' self-organized criticality in a river system is difficult without an extensive survey through space, whereas the recognition of sediment links requires quite intense sampling in specific river regions. We suggest that these separations between measurement scales represent an incommensurability issue in river studies, making it very difficult to both communicate among and test between two or more competing theories. Making simultaneous hyperscale observations of the river is one approach to minimizing the theory-ladeness of observation, as deviations from different predictions can be plotted at every scale. Copyright (C) 2010 John Wiley & Sons, Ltd.
BibTeX: @article{Fonstad2010, author = {Fonstad, MA and Marcus, WA}, title = {High resolution, basin extent observations and implications for understanding river form and process}, journal = {Earth Surface Processes and Landforms}, year = {2010}, volume = {35}, number = {6}, pages = {680--698} }
Fonstad2005	Fonstad, M. & Marcus, W.	Remote sensing of stream depths with hydraulically assisted bathymetry (HAB) models [Abstract] [BibTeX] [PDF]	2005	Geomorphology Vol. 72 (1-4) , pp. 320-339	article	remote sensing fluvial geomorphology
Abstract: This article introduces a technique for using a combination of remote sensing imagery and open-channel flow principles to estimate depths for each pixel in an imaged river. This technique, which we term hydraulically assisted bathymetry (HAB), uses a combination of local stream gage information on discharge, image brightness data, and Manning-based estimates of stream resistance to calculate water depth. The HAB technique does not require ground-truth depth information at the time of flight. HAB can be accomplished with multispectral or hyperspectral data, and therefore can be applied over entire watersheds using standard high spatial resolution satellite or aerial images. HAB also has the potential to be applied retroactively to historic imagery, allowing researchers to map temporal changes in depth. We present two versions of the technique, HAB-1 and HAB-2. HAB-1 is based primarily on the geometry, discharge and velocity relationships of river channels. Manning's equation (assuming average depth approximates the hydraulic radius), the discharge equation, and the assumption that the frequency distribution of depths within a cross-section approximates that of a triangle are combined with discharge data from a local station, width measurements from imagery, and slope measurements from maps to estimate minimum, average and maximum depths at a multiple cross-sections. These depths are assigned to pixels of maximum, average, and minimum brightness within the cross-sections to develop a brightness-depth relation to estimate depths throughout the remainder of the river. HAB-2 is similar to HAB-1 in operation, but the assumption that the distribution of depths approximates that of a triangle is replaced by an optical Beer-Lambert law of light absorbance. In this case, the flow equations and the optical equations are used to iteratively scale the river pixel values until their depths produce a discharge that matches that of a nearby gage. R-2 values for measured depths versus depths estimated by FLAB-I and HAB-2 are 0.51 and 0.77, respectively, in the relatively simple Brazos River, Texas R-2 values for HAB-1 and HAB-2 are 0.46 and 0.26, respectively, in the Lamar River, a complex mountain river system in Yellowstone National Park. Although the R-2 values are moderate, depth maps and cross-sections derived from the HAB techniques are consistent with typical stream geomorphology patterns and provide far greater spatial coverage and detail than could be achieved with ground-based survey techniques. Improved depth estimates can be achieved by stratifying the river into different habitat types that normalize for differences in turbulence and substrate. (c) 2005 Elsevier B.V. All rights reserved.
BibTeX: @article{Fonstad2005, author = {Fonstad, MA and Marcus, WA}, title = {Remote sensing of stream depths with hydraulically assisted bathymetry (HAB) models}, journal = {Geomorphology}, year = {2005}, volume = {72}, number = {1-4}, pages = {320--339} }
Fonstad2003	Fonstad, M. & Marcus, W.	Self-organized criticality in riverbank systems [Abstract] [BibTeX] [PDF]	2003	Annals of the Association of American Geographers Vol. 93 (2) , pp. 281-296	article	fluvial geomorphology
Abstract: Where and when do natural rivers become unstable? To answer this question, we visually estimated bank-failure extent in 100-m increments along 180 km of riverbanks in three watersheds of the northern Yellowstone ecosystem. The riverbank data reveal precise power-law relationships between the number of bank failures of a given size throughout each watershed and the magnitude of those bank failures. The slopes of log-log graphs (i.e., the exponent tau) of bank-failure magnitude versus failure frequency in alluvial reaches vary from 1.07 to 1.44, while tau for all reaches combined (alluvial, colluvial, and bedrock) varies from 1.18 to 1.53, suggesting that lower-gradient, alluvial streams are more susceptible to large bank failures. Cellular automata simulations of riverbanks show similar power-law failure relationships, as do bank-erosion data from a long-term independent dataset from another location. These power-law structures can be interpreted as the spatial signal of a self-organized critical (SOC) system, in which local instabilities function to generate broader-scale order. SOC systems are considered to be at the "edge of chaos," where local processes interact to make prediction of specific failure events impossible, although probability distribution prediction of the magnitude and spatial frequency of those events is possible. A critical structure of this sort is to be expected in bank failures along a stream given a nonlinear diffusive system such as a drainage basin. If riverbanks are, in fact, part of a critical system, then long-term local or watershed-wide stability is an unlikely or even impossible engineering or restoration goal. The existence of criticality in natural stream settings suggests that local human alterations designed to increase channel stability, while changing the local frequency of small failures, will only encourage an increase in the magnitude of system-wide, low-frequency large failures. A restoration or stabilization effort will not eliminate the bank instability. Instead, it will transfer that instability to neighboring riverbank areas.
BibTeX: @article{Fonstad2003, author = {Fonstad, M and Marcus, WA}, title = {Self-organized criticality in riverbank systems}, journal = {Annals of the Association of American Geographers}, year = {2003}, volume = {93}, number = {2}, pages = {281--296} }
Gavin2009a	Gavin, D.	The coastal-disjunct mesic flora in the inland Pacific Northwest of USA and Canada: refugia, dispersal and disequilibrium [Abstract] [BibTeX] [PDF]	2009	Diversity and Distributions Vol. 15 (6) , pp. 972-982	article	vegetation and climate
Abstract: Aim Understanding the history of the mesic-adapted plant species of eastern British Columbia and northern Idaho, disjunct from their main coastal distribution, may suggest how biotas reorganize in the face of climate change and dispersal barriers. For different species, current evidence supports establishment of the disjunction via an inland glacial refugium, via recent dispersal from the coast, or via a combination of both. In this study, the modern distributions of the coastal-disjunct vascular plants are analysed with respect to modern climate to examine how refugia and/or dispersal limitation control regional patterns in species richness. Location North-west North America. Methods The distributions of nine tree and 58 understorey species with a coastal-disjunct pattern were compiled on a 50-km grid. The relationship between species richness and an estimate of available moisture was calculated separately for formerly glaciated and unglaciated portions of the coastal and inland regions. Growth habit and dispersal mode were assessed as possible explanatory variables for species distributions. Results Species richness shows a strong relationship to climate in coastal-unglaciated areas but no relationship to climate in inland-glaciated areas. In inland-glaciated areas, richness is c. 70% lower than that expected from climate. Species with animal-dispersed seeds occupy a larger portion of coastal and inland regions than species with less dispersal potential. Main conclusions Modern patterns of diversity are consistent with both refugia and dispersal processes in establishing the coastal-disjunct pattern. The inland glacial refugium is marked by locally high diversity and several co-distributed endemics. In the inland-glaciated area, dispersal limitation has constrained diversity despite the nearby refugia. Onset of mesic climate within only the last 3000 years and the low dispersal capacity of many species in the refugium may explain this pattern. This study suggests that vascular plant species will face significant challenges responding to climate change on fragmented landscapes.
BibTeX: @article{Gavin2009a, author = {Gavin, DG}, title = {The coastal-disjunct mesic flora in the inland Pacific Northwest of USA and Canada: refugia, dispersal and disequilibrium}, journal = {Diversity and Distributions}, year = {2009}, volume = {15}, number = {6}, pages = {972--982} }
Gavin2003c	Gavin, D.	Forest soil disturbance intervals inferred from soil charcoal radiocarbon dates [Abstract] [BibTeX] [PDF]	2003	Canadian Journal of Forest Research Vol. 33 (12) , pp. 2514-2518	article
Abstract: Forest soil disturbance intervals are usually too long to measure using plot-based studies, and thus they are poorly understood. The mean soil disturbance interval (MSDI) in an old-growth forest on the west coast of Vancouver Island was estimated from radiocarbon dates of charcoal from organic and mineral soil horizons. Two assumptions are required to estimate the MSDI: (1) charcoal from forest fires is deposited within the organic horizon and eventually mixed into deeper mineral horizons by soil disturbances, and (2) the probability of soil disturbance is spatially homogeneous and affected only by the time since the last fire or the last soil disturbance. The MSDI is then estimated by the rate at which the proportion of undisturbed sample sites (determined by the proportion of sites with charcoal from the most recent fire in the organic horizon) decreases with increasing time since the last fire. Soil charcoal evidence of time since fire was determined at 83 sites using 141 radiocarbon dates. The estimated MSDI was greater on slopes (ca. 2010 years) than on terraces (ca. 920 years). The long periods between soil disturbances, especially on slopes, are consistent with other evidence from the study area that suggests infrequent tree uprooting is the predominant mode of soil disturbance.
BibTeX: @article{Gavin2003c, author = {Gavin, DG}, title = {Forest soil disturbance intervals inferred from soil charcoal radiocarbon dates}, journal = {Canadian Journal of Forest Research}, year = {2003}, volume = {33}, number = {12}, pages = {2514--2518} }
Gavin2001	Gavin, D.	Estimation of inbuilt age in radiocarbon ages of soil charcoal for fire history studies [Abstract] [BibTeX] [PDF]	2001	Radiocarbon Vol. 43 (1) , pp. 27-44	article
Abstract: Radiocarbon age determinations of wood charcoal are commonly used to date past forest fire events, even though such ages should be greater than the fire event due to the age of the wood at the time of burning. The difference in the C-14-derived age of charcoal and the time-since-fire (the "inbuilt age") may be considerable in some vegetation types and thus must be estimated before interpreting fire dates. Two methods were used to estimate the potential range of inbuilt age of soil charcoal dated to determine ages of forest fires on the west coast of Vancouver Island (Canada). First, 26 C-14 ages on charcoal in surficial soil were compared directly with ages of forest fire determined by tree-ring counts, suggesting inbuilt ages of 0-670 years. Second, a simulation model that uses estimated fuel loads, fuel consumption, charcoal production, and the ages of charred wood (time since wood formation), suggests that the combination of slow growth rates and slow decay rates of certain species can account for inbuilt ages of more than 400 years in this forest type. This level of inbuilt age is large enough such that the actual age of a fire may not occur within the 2 sigma confidence interval of a calibrated charcoal C-14 age determination, and thus significantly affect the interpretation of fire dates. A method is presented to combine the error of a calibrated C-14 age determination with the error due to inbuilt age such that the larger adjusted error encompasses the actual age of the fire.
BibTeX: @article{Gavin2001, author = {Gavin, DG}, title = {Estimation of inbuilt age in radiocarbon ages of soil charcoal for fire history studies}, journal = {Radiocarbon}, year = {2001}, volume = {43}, number = {1}, pages = {27--44} }
Gavin2008	Gavin, D.; Beckage, B. & Osborne, B.	Forest dynamics and the growth decline of red spruce and sugar maple on Bolton Mountain, Vermont: a comparison of modeling methods [Abstract] [BibTeX] [PDF]	2008	Canadian Journal of Forest Research Vol. 38 (10) , pp. 2635-2649	article
Abstract: Montane forests in the northeastern United States have experienced symptoms of declining vigor, such as branch dieback and increased mortality, over the last half-century. These declines have been attributed to the cumulative impacts of acid deposition, but reconstructing these declines from tree-ring records has proved difficult because of confounding factors that affect low-frequency growth patterns, including climate and natural growth trajectories following disturbance. We obtained tree-ring records of red spruce (Picea rubens Sarg.) and sugar maple (Acer saccharum L.) from three elevations on Bolton Mountain, Vermont, and applied traditional dendroclimatological analyses that revealed a profound declining growth-climate correlation since ca. 1970 for sugar maple but much less so for red spruce. We then applied a new multifaceted statistical approach that conservatively detrends tree-ring records by minimizing the influences of tree size, age, and canopy disturbances on radial growth. In contrast with the traditional analysis, this approach yielded chronologies that were consistently correlated with climate but with important exceptions. Low-elevation sugar maple suffered distinct episodes of slow growth, likely because of insect defoliators, and also a progressive decline since ca. 1988. Red spruce experienced subdecadal episodes of decline that may be related to freeze-thaw events known to injure foliage but showed no evidence of a progressive decline. This analysis was supported by a forest plot resurvey that indicated major declines in these species.
BibTeX: @article{Gavin2008, author = {Gavin, DG and Beckage, B and Osborne, B}, title = {Forest dynamics and the growth decline of red spruce and sugar maple on Bolton Mountain, Vermont: a comparison of modeling methods}, journal = {Canadian Journal of Forest Research}, year = {2008}, volume = {38}, number = {10}, pages = {2635--2649} }
Gavin1999	Gavin, D. & Brubaker, L.	A 6000-year soil pollen record of subalpine meadow vegetation in the Olympic Mountains, Washington, USA [Abstract] [BibTeX] [PDF]	1999	Journal of Ecology Vol. 87 (1) , pp. 106-122	article
Abstract: 1 Subalpine meadow communities are influenced by edaphic and microclimatic gradients, and should be affected by climate change that affects these local controls. We used pollen preserved in meadow soils to investigate the long-term interaction of these factors in a 1-ha subalpine meadow in the Olympic Mountains, Washington, USA. 2 To describe the spatial scale at which soil pollen is related to neighbouring vegetation, pollen in 46 soil surface samples was compared with plant cover within concentric circular plots (0.5-1 m radii). Regression analysis of percentage pollen with plant cover at different distances from the surface sample had the highest correlation with radii < 1 m, confirming that entomophilous meadow species have very small relevant pollen source areas. 3 We analysed pollen records in soil columns at three sites representing a range of growing season lengths and community types within the meadow. Soils had aggraded by the deposition of eolian silt. Radiocarbon dates of pollen concentrates were similar to or older than radiocarbon dates on charcoal pieces at the same depth, suggesting negligible downwards movement of pollen in the soil profile. 4 The oldest soil pollen profile was from the wettest microsite, currently dominated by a snowbed Carex nigricans community. This site was occupied by a dry Juniperus community prior to c. 6000 BP (before present), when it shifted to more mesic communities dominated by Poaceae and Polemonium. The first appearance of a snowbed Calex nigricans community at this site, c, 2500-1500 BP suggests a change to cooler and/or wetter regional climate. 5 High levels of Polygonum bistortoides at all sites indicated a shift to long snow-free periods and mesic summer conditions during an interval corresponding to the Medieval Warm Period (c. 1200-700 BP). After 500 BP (during the Little Ice Age) Carex nigricans re-established in the wet microsite, while relatively little change occurred at the other two sites. Overall, the greater magnitude of change at this microsite than at the longer growing-season sites indicates that, in these subalpine meadows, short growing season sites are most sensitive to regional climate change.
BibTeX: @article{Gavin1999, author = {Gavin, DG and Brubaker, LB}, title = {A 6000-year soil pollen record of subalpine meadow vegetation in the Olympic Mountains, Washington, USA}, journal = {Journal of Ecology}, year = {1999}, volume = {87}, number = {1}, pages = {106--122} }
Gavin2003a	Gavin, D.; Brubaker, L. & Lertzman, K.	An 1800-year record of the spatial and temporal distribution of fire from the west coast of Vancouver Island, Canada [Abstract] [BibTeX] [PDF]	2003	Canadian Journal of Forest Research Vol. 33 (4) , pp. 573-586	article
Abstract: Charcoal records from lake sediments may show changes in fire frequency over thousands of years, but such records are ambiguous with regard to the actual locations of fires. Using a comparison of fire dates from an 1800-year lake sediment record from the west coast of Vancouver Island (British Columbia, Canada) and dates of last fire from 38 sites in the same watershed using tree-ring and soil-charcoal C-14 dates, we estimated the source area that contributes to charcoal peaks and determined the degree to which fires were biased to certain locations. Twenty-three charcoal peaks, likely corresponding with individual fire events, were objectively identified from the sediment record. Comparison of fire dates from charcoal peaks in the sediment record with fire dates from points near the lake suggests that the charcoal source area is within 500 m of the lake edge. Fire occurrence within this charcoal source area increased sharply at AD 1100 from ca. 50 to ca. 300 years between charcoal peaks, coeval with the first "Little Ice Age" cooling. Soil-charcoal radiocarbon dates revealed that 37% of the charcoal source area had not burned over the last 1800 years and that the 23 fires identified in the sediment record were restricted to south-facing slopes near the lake. This spatial pattern may result only if fire is >25 times more likely to occur on susceptible sites (south-facing slopes) than on less susceptible sites. This strong bias in fire location ensured the millennial-scale persistence of large areas of late-successional forest through past climatic periods.
BibTeX: @article{Gavin2003a, author = {Gavin, DG and Brubaker, LB and Lertzman, KP}, title = {An 1800-year record of the spatial and temporal distribution of fire from the west coast of Vancouver Island, Canada}, journal = {Canadian Journal of Forest Research}, year = {2003}, volume = {33}, number = {4}, pages = {573--586} }
Gavin2003b	Gavin, D.; Brubaker, L. & Lertzman, K.	Holocene fire history of a coastal temperate rain forest based on soil charcoal radiocarbon dates [Abstract] [BibTeX] [PDF]	2003	Ecology Vol. 84 (1) , pp. 186-201	article
Abstract: The long-term role of fire in coastal temperate rain forest is poorly understood. To determine the historical role of fire on western Vancouver Island (British Columbia, Canada), we constructed a long-term spatially explicit fire history and examined the spatial and temporal distribution of fire during the Holocene. Two fire-history parameters (time-since-fire [TSF] and fire extent) were related to three landscape parameters landform [hill slope or terrace]. aspect, and forest composition) at 83 sites in a 730-ha low-elevation (less than similar to200 m) area of a mountainous watershed. We dated fires using tree rings ( 18 sites) and 120 soil-charcoal radiocarbon dates (65 sites). Comparisons among multiple radiocarbon dates indicated a high probability that the charcoal dated at each site represented the most recent fire, though we expect greater error in TSF estimates at sites where charcoal was very old (>6000 yr) and was restricted to mineral soil horizons. TSF estimates ranged from 64 to similar to12 220 yr; 45% of the sites have burned in the last 1000 yr, whereas 2017( of the sites have not burned for over 6000 yr. Differences in median TSF were more significant between landform types or across aspects than among forest types, Median TSF was significantly greater on terraces (4410 yr) than on hill slopes (740 yr). On hill slopes. all south-facing and southwest-facing sites have burned within the last 1000 yr compared to only 27% of north- and east-facing sites burning over the same period. Comparison of fire dates among neighboring sites indicated that fires rarely extended >250 m. During the late Holocene, landform controls have been strong. resulting in the bias of fires to south-facing hillslopes and thus allowing late-successional forest structure to persist for thousands of years in a large portion of the watershed. In contrast, the early Holocene regional climate and forest composition likely resulted in larger landscape tires that were not strongly controlled by landform factors. The millennial-scale TSF detected in this study supports the distinction of coastal temperate rain forest as being under a fundamentally different disturbance regime than other Pacific Northwest forests to the cast and south.
BibTeX: @article{Gavin2003b, author = {Gavin, DG and Brubaker, LB and Lertzman, KP}, title = {Holocene fire history of a coastal temperate rain forest based on soil charcoal radiocarbon dates}, journal = {Ecology}, year = {2003}, volume = {84}, number = {1}, pages = {186--201} }
Gavin2005a	Gavin, D.; Brubaker, L.; McLachlan, J. & Oswald, W.	Correspondence of pollen assemblages with forest zones across steep environmental gradients, Olympic Peninsula, Washington, USA [Abstract] [BibTeX] [PDF]	2005	Holocene Vol. 15 (5) , pp. 648-662	article	vegetation and climate
Abstract: The use of pollen records to document vegetation responses to climatic change in mountains relies on the ability of pollen assemblages to differentiate among elevationally stratified vegetation zones. Comparisons among modern pollen assemblages within mountainous areas provide a basis for assessing this potential. We examined relationships between pollen assemblages, forest vegetation and climate at 65 small lake sites distributed across five forest zones on the Olympic Peninsula, Washington. Sample sites spanned nearly the full range of climatic gradients on the Peninsula, e. 900-6000 mm annual precipitation and c. 17-8 degrees C July mean temperature (from 9 to 1981 m a.s.l.). The pollen percentages of most arboreal taxa showed a strong relationship with elevation, especially for taxa with poor dispersal potential (Abies and Picea) or high elevation ranges (Tsuga mertensiana and Alnus sinuata). Tsuga heterophylla was the only pollen taxon abundant across all forest zones. Both detrended correspondence analysis (DCA) and linear discriminant analysis (DA) arranged pollen assemblages along temperature and precipitation gradients approximating the actual distribution of vegetation along these gradients. DA classified 90%, of the sites into their correct forest zones, but was very sensitive to sample size, suggesting that caution should be exercised when using DA for classifying fossil pollen assemblages. Pairwise comparisons using the squared-chord-distance metric (SCD) showed that the SCD threshold that best distinguishes neighbouring forest zones is affected by the number of samples in each forest zone and by the patchiness of species distributions within each zone, suggesting that SCD is also sensitive to sample size and that thresholds used with the modern analogue technique must be calibrated for each vegetation zone. This study indicates that pollen assemblages on the Olympic Peninsula record local forest zones despite steep environmental gradients and the close proximity of neighbouring forest zones.
BibTeX: @article{Gavin2005a, author = {Gavin, DG and Brubaker, LB and McLachlan, JS and Oswald, WW}, title = {Correspondence of pollen assemblages with forest zones across steep environmental gradients, Olympic Peninsula, Washington, USA}, journal = {Holocene}, year = {2005}, volume = {15}, number = {5}, pages = {648--662} }
Gavin2007	Gavin, D.; Hallett, D.; Hu, F.; Lertzman, K.; Prichard, S.; Brown, K.; Lynch, J.; Bartlein, P. & Peterson, D.	Forest fire and climate change in western North America: insights from sediment charcoal records [Abstract] [BibTeX] [PDF]	2007	Frontiers in Ecology and the Environment Vol. 5 (9) , pp. 499-506	article
Abstract: Millennial-scale records of forest fire provide important baseline information for ecosystem management, especially in regions with too few recent fires to describe the historical range of variability. Charcoal records from lake sediments and soil profiles are well suited for reconstructing the incidence of past fire and its relationship to changing climate and vegetation. We highlight several records from western North America and their relevance in reconstructing historical forest dynamics, fire-climate relationships, and feedbacks between vegetation and fire under climate change. Climatic effects on fire regimes are evident in many regions, but comparisons of paleo-fire records sometimes show a lack of synchrony, indicating that local factors substantially affect fire occurrence, even over long periods. Furthermore, the specific impacts of vegetation change on fire regimes vary among regions with different vegetation histories. By documenting the effects on fire patterns of major changes in climate and vegetation, paleo-fire records can be used to test the mechanistic models required for the prediction of future variations in fire.
BibTeX: @article{Gavin2007, author = {Gavin, DG and Hallett, DJ and Hu, FS and Lertzman, KP and Prichard, SJ and Brown, KJ and Lynch, JA and Bartlein, P and Peterson, DL}, title = {Forest fire and climate change in western North America: insights from sediment charcoal records}, journal = {Frontiers in Ecology and the Environment}, year = {2007}, volume = {5}, number = {9}, pages = {499--506} }
Gavin2011	Gavin, D.; Henderson, A.; Westover, K.; Fritz, S.; Walker, I.; Leng, M. & Hu, F.	Abrubt Holocene climate change and potential response to solar forcing in western Canada [Abstract] [BibTeX]	2011	Quaternary Science Reviews , pp. -	article
Abstract: Several abrupt climate events during the Holocene, including the widely documented oscillation at 8.2 thousand years before present (ka), are attributed to changes in the North Atlantic thermohaline circulation. Additional mechanisms, such as interactions between atmospheric circulation, ice-sheet dynamics, and the influence of solar irradiance, also have been proposed to explain abrupt climatic events, but evidence remains elusive. This study presents evidence from multi-proxy analyses on the Holocene sediments of Eleanor Lake, interior British Columbia. Climatic inferences from our decadal-resolution record of biogenic silica (BSi) abundance are supported by changes in diatom and pollen assemblages from the same core and correlations with existing regional climate records. The BSi record reveals abrupt and persistent climatic shifts at 10.2, 9.3, and 8.5 ka, the latter two of which are coeval with major collapses of the Laurentide Ice Sheet. The record also reveals a short-term cooling at 8.2 ka that is distinct from the 8.5 ka event and similar in magnitude to several other late-Holocene coolings. BSi is correlated with solar-irradiance indices (r=0.43-0.61), but the correlation is opposite in sign to that expected from direct solar forcing and weakens after 8 ka. Possible mechanisms causing the abrupt and persistent climate changes of the early Holocene include 1) sudden losses of ice and proglacial lake extent, causing a shift in the meridional structure of atmospheric circulation, 2) a possible link between solar minima and El Niño-like conditions that are correlated with warm spring temperature in interior British Columbia, and 3) the influence of solar irradiance variability on the position of the polar jet, possibly via effects on the strength of the glacial anticyclone.
BibTeX: @article{Gavin2011, author = {Gavin, DG and Henderson, ACG and Westover, K and Fritz, SC and Walker, IR and Leng, MJ and Hu, FS}, title = {Abrubt Holocene climate change and potential response to solar forcing in western Canada}, journal = {Quaternary Science Reviews}, year = {2011}, pages = {--} }
Gavin2006	Gavin, D. & Hu, F.	Spatial variation of climatic and non-climatic controls on species distribution: the range limit of Tsuga heterophylla [Abstract] [BibTeX] [PDF]	2006	Journal of Biogeography Vol. 33 (8) , pp. 1384-1396	article
Abstract: Aim: To assess which climatic variables control the distribution of western hemlock (Tsuga heterophylla), how climatic controls vary over latitude and between disjunct coastal and interior sub-distributions, and whether non-climatic factors, such as dispersal limitation and interspecific competition, affect range limits in areas of low climatic control. Location: North-western North America. Methods:We compared four bioclimatic variables [actual evapotranspiration (AET), water deficit (DEF), mean temperature of the coldest month (MTCO), and growing degree-days (GDD5)] with the distribution of T. heterophylla at a 2-km grid cell resolution. The distribution is based on a zonal ecosystem classification where T. heterophylla is the dominant late-successional species. For each bioclimatic variable and at each degree of latitude, we calculated the threshold that best defines the T. heterophylla distribution and assessed the extent to which T. heterophylla was segregated to one end of the bioclimatic gradient. We also fitted two forms of multivariate bioclimatic models to predict the T. heterophylla distribution: a simple threshold model and a complex Gaussian mixture model. Each model was trained separately on the coastal and interior distributions, and predicted areas outside of the T. heterophylla distribution (overprediction) were evaluated with respect to known outlier populations. Results: Actual evapotranspiration was the most accurate predictor across the T. heterophylla distribution; other variables were important only in certain areas. There was strong latitudinal variation in the thresholds of all variables except AET, and the interior distribution had wider bioclimatic thresholds than the coastal distribution. The coastal distribution was predicted accurately by both bioclimatic models; areas of overprediction rarely occurred > 10 km from the observed distribution and generally matched small outlier populations. In contrast, the interior distribution was poorly predicted by both models; areas of overprediction occurred up to 140 km from the observed distribution and did not match outlier populations. The greatest overprediction occurred in Idaho and Montana in areas supporting species that typically co-exist with T. heterophylla. Main conclusions: The high predictive capacity of AET is consistent with this species' physiological requirements for a mild and humid climate. Spatial variation of MTCO, GDD5 and DEF thresholds probably reflects both the correlation of these variables with AET and ecotypic variation. The level of overprediction in portions of the interior suggests that T. heterophylla has not completely expanded into its potential habitat. Tsuga heterophylla became common in the interior 2000-3500 years ago, compared with > 9000 years ago in the coastal region. The limited time for dispersal, coupled with frequent fires at the margins of the distribution and competition with disturbance-adapted species, may have retarded range expansion in the interior. This study demonstrates that bioclimatic modelling can help identify various climatic and non-climatic controls on species distributions.
BibTeX: @article{Gavin2006, author = {Gavin, DG and Hu, FS}, title = {Spatial variation of climatic and non-climatic controls on species distribution: the range limit of Tsuga heterophylla}, journal = {Journal of Biogeography}, year = {2006}, volume = {33}, number = {8}, pages = {1384--1396} }
Gavin2005	Gavin, D. & Hu, F.	Bioclimatic modelling using Gaussian mixture distributions and multiscale segmentation [Abstract] [BibTeX] [PDF]	2005	Global Ecology and Biogeography Vol. 14 (5) , pp. 491-501	article
Abstract: Aim To introduce Gaussian mixture distributions and sequential maximum a posteriori image segmentation (GM-SMAP) as a model that predicts species ranges from mapped climatic variables, and to compare its predictive capacity with two commonly used bioclimatic models: regression tree analysis (RTA) and smoothed response surfaces (SRS). Location North-west North America. Methods We compared models for their ability to predict the distributional range of western hemlock (Tsuga heterophylla). We calculated and projected nine climatic and water-balance variables to a 2-km grid up to 140 km from the T. heterophylla range. Models were trained using the five variables selected by RTA, as well as subsets of three variables. Goodness of fit was assessed using models trained and tested on the entire study area. Predictive capacity was assessed using 100 cross-validation tests, each trained on a randomly sampled 1% of the study area and tested on the complement of the study area. Results Models using all five variables were significantly better than three-variable models. Model fit was greatest for SRS. GM-SMAP misclassified slightly more area and RTA misclassified almost twice the area compared to SRS. However, cross- validation showed that the predictive capacity was clearly greatest for GM-SMAP and lowest for SRS, indicating that GM-SMAP makes more accurate predictions from sparse data. Main conclusions GM distributions prevent overfitting using an information-theoretic approach, and the SMAP algorithm minimizes the spatial extent of the largest misclassified area using a multiscale method. These properties, useful for image classification, also aid their strong predictive capacity as a bioclimatic model. SRS overfit the data, lowering its predictive capacity, and RTA failed to capture details of interactions among variables, yielding a poor fit. These results demonstrate the strong potential of GM-SMAP as a bioclimatic model.
BibTeX: @article{Gavin2005, author = {Gavin, DG and Hu, FS}, title = {Bioclimatic modelling using Gaussian mixture distributions and multiscale segmentation}, journal = {Global Ecology and Biogeography}, year = {2005}, volume = {14}, number = {5}, pages = {491--501} }
Gavin2006a	Gavin, D.; Hu, F.; Lertzman, K. & Corbett, P.	Weak climatic control of stand-scale fire history during the late Holocene [Abstract] [BibTeX] [PDF]	2006	Ecology Vol. 87 (7) , pp. 1722-1732	article
Abstract: Forest fire occurrence is affected by multiple controls that operate at local to regional scales. At the spatial scale of forest stands, regional climatic controls may be obscured by local controls (e.g., stochastic ignitions, topography, and fuel loads), but the long-term role of such local controls is poorly understood. We report here stand-scale (< 100 ha) fire histories of the past 5000 years based on the analysis of sediment charcoal at two lakes I I km apart in southeastern British Columbia. The two lakes are today located in similar subalpine forests, and they likely have experienced the same late-Holocene climatic. changes because of their close proximity. We evaluated two independent properties of fire history: (1) fire-interval distribution, a measure of the overall incidence of fire, and (2) fire synchroneity, a measure of the co-occurrence of fire (here, assessed at centennial to millennial time scales due to the resolution of sediment records). Fire-interval distributions differed between the sites prior to, but not after, 2500 yr before present. When the entire 5000-yr period is considered, no statistical synchrony between fire-episode dates existed between the two sites at any temporal scale, but for the last 2500 yr marginal levels of synchrony occurred at centennial scales. Each individual fire record exhibited little coherency with regional climate changes. In contrast, variations in the composite record (average of both sites) matched variations in climate evidenced by late-Holocene glacial advances. This was probably due to the increased sample size and spatial extent represented by the composite record (up to 200 ha) plus increased regional climatic variability over the last several millennia, which may have partially overridden local, non-climatic controls. We conclude that (1) over past millennia, neighboring stands with similar modern conditions may have experienced different fire intervals and asynchronous patterns in fire episodes, likely because local controls outweighed the synchronizing effect of climate; (2) the influence of climate on fire occurrence is more strongly expressed when climatic variability is relatively great; and (3) multiple records from a region are essential if climate-fire relations are to be reliably described.
BibTeX: @article{Gavin2006a, author = {Gavin, DG and Hu, FS and Lertzman, K and Corbett, P}, title = {Weak climatic control of stand-scale fire history during the late Holocene}, journal = {Ecology}, year = {2006}, volume = {87}, number = {7}, pages = {1722--1732} }
Gavin2009	Gavin, D.; Hu, F.; Walker, I. & Westover, K.	The northern inland temperate rainforest of British Columbia: old forests with a young history? [Abstract] [BibTeX] [PDF]	2009	Northwest Science Vol. 83 (1) , pp. 70-78	article
Abstract: The inland temperate rainforest (ITR) in east-central British Columbia is marked by superlative examples of old-growth cedar-hemlock forest. How long has this old-growth forest structure been a major component of this landscape? What is the biological and conservation significance of the history of this forest type? Here we present paleoecological evidence from a study in the Robson Valley of the Upper Fraser River. Sediment cores from Gerry Lake and Redmountain Lake show that western hemlock and western redcedar increased in abundance only within the last 2000 years. Thus, the old-growth forests of the northern ITR may have been present for only a few generations of trees. It is even possible, based on our preliminary evidence, that the oldest western redcedar in these stands may be the first colonizing individuals at these sites. Further paleoecological studies, including a combination of stand-age structure and pollen analysis from small lakes and forest hollows, are needed in order to understand the historical significance of these stands. A recent establishment of the ITR has implications for understanding the assembly of the modern diverse biota of the region as well as how the biota will respond to future climate change.
BibTeX: @article{Gavin2009, author = {Gavin, DG and Hu, FS and Walker, IR and Westover, K}, title = {The northern inland temperate rainforest of British Columbia: old forests with a young history?}, journal = {Northwest Science}, year = {2009}, volume = {83}, number = {1}, pages = {70--78} }
Gavin2001a	Gavin, D.; McLachlan, J.; Brubaker, L. & Young, K.	Postglacial history of subalpine forests, Olympic Peninsula, Washington, USA [Abstract] [BibTeX] [PDF]	2001	Holocene Vol. 11 (2) , pp. 177-188	article
Abstract: To investigate subalpine vegetation history on the Olympic Peninsula, Washington (USA), two pollen, macrofossil and charcoal records were studied in climatically distinct zones: Martins Lake (1415 m) in the moist Tsuga mertensiana zone and Moose Lake (1508 m) in the drier Abies lasiocarpa zone. The interpretation of fossil pollen assemblages was aided by comparisons with 308 modern assemblages from the Olympic Peninsula and western North America. Both pollen records show a cold/dry period following deglaciation (>10000 radiocarbon years BP) with sparse tundra and little similarity to any modern pollen assemblage. In the early Holocene, when summer temperatures are thought to have been higher than present, high percentages of Alnus sinuata-type pollen at both lakes suggest increased avalanche activity. At Martins Lake warmer summers were not accompanied by forest establishment, possibly because persistent spring snow pack, snow avalanches, and/or edaphic constraints limited tree establishment at this site. The Martins Lake record shows a steplike shift in vegetation to modern Tsuga mertensiana/Abies amabilis parkland across the Mazama tephra (6730 BP). In contrast to Martins Lake, Abies lasiocarpa forest quickly established at Moose Lake in the early Holocene, though forests were probably initially open and fires may have been frequent. From 7800 to 5100 BP forests near Moose Lake shifted gradually to cooler and moister species composition, with the addition of Chamaecyparis nootkatensis, Tsuga mertensiana and Pinus, though Abies lasiocarpa remained dominant. Forest cover was probably greatest during this transition, with parklike conditions at Moose Lake beginning at c. 5100 BP. The major differences in the records between the two sites may be due to differences in the local expression of regional climatic change and/or differences in soil development and stabilization.
BibTeX: @article{Gavin2001a, author = {Gavin, DG and McLachlan, JS and Brubaker, LB and Young, KA}, title = {Postglacial history of subalpine forests, Olympic Peninsula, Washington, USA}, journal = {Holocene}, year = {2001}, volume = {11}, number = {2}, pages = {177--188} }
Gavin2003	Gavin, D.; Oswald, W.; Wahl, E. & Williams, J.	A statistical approach to evaluating distance metrics and analog assignments for pollen records [Abstract] [BibTeX] [PDF]	2003	Quaternary Research Vol. 60 (3) , pp. 356-367	article	modern climate analoguesm
Abstract: The modern analog technique typically uses a distance metric to determine the dissimilarity between fossil and modern biological assemblages. Despite this quantitative approach, interpretation of distance metrics is usually qualitative and rules for selection of analogs tend to be ad hoe. We present a statistical tool, the receiver operating characteristic (ROC) curve, which provides a framework for identifying analogs from distance metrics. If modern assemblages are placed into groups (e.g., biomes), this method can (1) evaluate the ability of different distance metrics to distinguish among groups, (2) objectively identify thresholds of the distance metric for determining analogs, and (3) compute a likelihood ratio and a Bayesian probability that a modern group is an analog for an unknown (fossil) assemblage. Applied to a set of 1689 modern pollen assemblages from eastern North America classified into eight biomes, ROC analysis confirmed that the squared-chord distance (SCD) outperforms most other distance metrics. The optimal threshold increased when more dissimilar biomes were compared. The probability of an analog vs no-analog result (a likelihood ratio) increased sharply when SCD decreased below the optimal threshold, indicating a nonlinear relationship between SCD and the probability of analog. Probabilities of analog computed for a postglacial pollen record at Tannersville Bog (Pennsylvania, USA) identified transitions between biomes and periods of no analog. (C) 2003 Elsevier Science (USA). Published by Elsevier Inc. All rights reserved.
BibTeX: @article{Gavin2003, author = {Gavin, DG and Oswald, WW and Wahl, ER and Williams, JW}, title = {A statistical approach to evaluating distance metrics and analog assignments for pollen records}, journal = {Quaternary Research}, year = {2003}, volume = {60}, number = {3}, pages = {356--367} }
Gavin1999a	Gavin, D. & Peart, D.	Vegetative life history of a dominant rain forest canopy tree [Abstract] [BibTeX] [PDF]	1999	Biotropica Vol. 31 (2) , pp. 288-294	article
Abstract: Tetramerista glabra has a remarkable combination of life history traits. it is a dense-wooded, large, common canopy tree in primary pear swamp rain forest. Its seedlings, although shade tolerant, can grow rapidly in high light conditions, but frequently lack structural stability Most juvenile stems (94% in the understory and 38% in canopy gaps) collapse under their own weight or from branchfalls. Fallen stems then ramify into vegetative sprouts, which in turn may collapse, perpetuating a vegetative juvenile cycle. Most recruitment is from sprouts rather than from seed. Structural analysis of stem dimensions shows that stems 2-8 cm DBH (diameter at breast height) are dose to the theoretical buckling limit, especially for those dependent on neighboring vegetation to maintain vertical form. Trees > 4 cm DBH persisting as upright stems develop stilt root support and become structurally independent at ca 8 cm DBH. Eventually, as stems thicken, stilt roots anastamose and trees adopt the cylindrical growth form of mature canopy trees (up to 150 cm DBH). Thus, the vegetative life history strategy of the species is to: (i) regenerate a large "ramet bank" from the majority of juveniles that fail structurally while suppressed in the understory, and (ii) to maximize height growth at the expense of diameter growth in high light conditions. The growth pattern and plastic form of I:glabra shows how a shade tolerant species may adapt to utilize the ephemeral light resource in canopy gaps. The growth strategy of this species allows it to circumvent the normal trade-off between shade tolerance and rapid growth in Canopy gaps.
BibTeX: @article{Gavin1999a, author = {Gavin, DG and Peart, DR}, title = {Vegetative life history of a dominant rain forest canopy tree}, journal = {Biotropica}, year = {1999}, volume = {31}, number = {2}, pages = {288--294} }
Gavin1997	Gavin, D. & Peart, D.	Spatial structure and regeneration of Tetramerista glabra in peat swamp rain forest in Indonesian Borneo [Abstract] [BibTeX] [PDF]	1997	Plant Ecology Vol. 131 (2) , pp. 223-231	article
Abstract: We examined the spatial structure and regeneration of Tetramerista glabra, a dominant canopy tree in peat swamp rain forest in Borneo (West Kalimantan, Indonesia). T. glabra has strong spatial structure that changes dramatically during the life cycle, seedlings were highly aggregated, saplings were random and trees were evenly distributed. Germination and seedling relative growth were highest within canopy gaps, but seedling densities were highest at gap edges. Concentration of seedlings in gap edges, rather than localized seed dispersal, was responsible for seedling patchiness. The slope of the relationship between relative growth rate and seedling height decreased from gap, to gap edge to understory habitats, suggesting that competition within the seedling layer is more important in gaps than in the understory. The processes that break down seedling aggregation, leading to over-dispersion of trees, must be density dependent, but remain unknown.
BibTeX: @article{Gavin1997, author = {Gavin, DG and Peart, DR}, title = {Spatial structure and regeneration of Tetramerista glabra in peat swamp rain forest in Indonesian Borneo}, journal = {Plant Ecology}, year = {1997}, volume = {131}, number = {2}, pages = {223--231} }
Gavin1993	Gavin, D. & Peart, D.	Effects of beech bark disease on the growth of american beech (Fagus grandifolia) [Abstract] [BibTeX]	1993	Canadian Journal of Forest Research Vol. 23 (8) , pp. 1566-1575	article
Abstract: We studied radial growth reduction in American beech (Fagus grandifolia Ehrh.) in relation to the level of defect induced by beech bark disease, in second-growth and old-growth northern hardwoods stands in New Hampshire. In the second-growth stand at Moose Mountain (n = 243 trees), 1989-1990 radial growth declined significantly with increasing severity of external symptoms. The severity of external symptoms increased significantly with DBH. To examine temporal trends, internal defect induced by the disease was quantified as the percentage of growth sheath cankered in each year, by cross-sectioning a subsample of 40 trees. Internal defect first appeared in 1950, increased through 1969, then declined until a major pulse of infection in the period 1983-1987. Sectioned trees were divided into infection classes based on a cumulative measure of internal defect. Growth of severely infected trees first fell below that of uninfected trees in 1965, and was consistently lower after 1972. The growth ratio of severely infected to uninfected trees generally declined from 1960 to 1990; by 1990, growth of severely infected trees was reduced by more than 40% relative to healthy trees. This decline in the growth ratio corresponded well to the increase in cumulative internal defect in the stand, suggesting that disease stress had cumulative effects on tree vigor. The relation between beech bark disease and growth was also examined on an individual-tree basis; recent growth decline was significantly greater for trees with higher levels of internal defect. Internal defect was a better predictor of growth trends than was external defect. External defect was only moderately correlated with internal defect (r2 = 0.503). In the old-growth stand at Bartlett. N.H. (n = 40 trees) infection was quantified from external symptoms only. As in the second-growth stand, the growth of severely infected trees in the old-growth stand fell significantly below that of uninfected trees. However, significant differences in growth between uninfected and severely infected trees occurred earlier in the old-growth stand, first appearing in 1949. Delayed growth reductions in the second-growth stand may be associated with changes in shade and moisture affecting the beech scale, changes in tree physiological stress after selective logging, or changes in the density of large trees. Beech may survive long periods of infection by beech bark disease. However, our results demonstrate clearly that beech bark disease has reduced the growth of American beech in both second-growth and old-growth northern hardwoods stands for several decades.
BibTeX: @article{Gavin1993, author = {Gavin, DG and Peart, DR}, title = {Effects of beech bark disease on the growth of american beech (Fagus grandifolia)}, journal = {Canadian Journal of Forest Research}, year = {1993}, volume = {23}, number = {8}, pages = {1566--1575} }
Goovaerts2005	Goovaerts, P.; Jacquez, G. & Marcus, W.	Geostatistical and local cluster analysis of high resolution hyperspectral imagery for detection of anomalies [BibTeX] [PDF]	2005	Remote Sensing of Environment Vol. 95 , pp. 351-367	article	remote sensing
BibTeX: @article{Goovaerts2005, author = {Goovaerts, P and Jacquez, GM and Marcus, WA}, title = {Geostatistical and local cluster analysis of high resolution hyperspectral imagery for detection of anomalies}, journal = {Remote Sensing of Environment}, year = {2005}, volume = {95}, pages = {351-367} }
Gritzner2001	Gritzner, M.; Marcus, W.; Aspinall, R. & Custer, S.	Assessing landslide potential using GIS, soil wetness modeling and topographic attributes, Payette River, Idaho [Abstract] [BibTeX]	2001	Geomorphology Vol. 37 (1-2) , pp. 149-165	article
Abstract: This study utilizes GIS modeling to determine if the location of 559 landslides in the 875 km(2) catchment of the Middle Fork of the Payette River, Idaho can be predicted based on topographic attributes and a wetness index generated by the DYNWET model. Slope and elevation were significantly related to landslide occurrence at this landscape scale. Aspect was also retained as a variable for further analysis because, despite a non-significant chi-square relation to landslide occurrence, graphical analysis suggested a relation between aspect and mass wasting. Chi-square analysis indicated that plan and profile curvature, flow path length, upslope contributing area. and the DYNWET-based moisture index were not significantly related to landsliding. A Bayesian probability model based on combinations of elevation, slope, aspect, and wetness indicates that elevation exhibits the closest relation to landsliding. followed by slope; but that neither aspect nor wetness index values help in prediction. The Bayesian probability model using elevation and slope generates a map of relative landslide risk that can be used to direct activities away from mass wasting prone areas, The association between elevation and landslides is perplexing but is perhaps due to the location of logging road at specific elevations (roads could not be included in the input data for analysis because they have not been adequately mapped). The lack of explanation provided by the DYNWET wetness index was also surprising and may be due to the 30-m digital elevation model (DEM) and the soils data having resolutions too coarse to adequately portray local variations key to mass wasting. We believe the inadequacy of data to drive the models is typical of the majority of catchment scale setting. For now, the ability of researchers to effectively model landscape scale landsliding is more limited by the type, resolution, and quality of available data than by the quality of the landslide models. (C) 2001 Elsevier Science B.V. All rights reserved.
BibTeX: @article{Gritzner2001, author = {Gritzner, ML and Marcus, WA and Aspinall, R and Custer, SG}, title = {Assessing landslide potential using GIS, soil wetness modeling and topographic attributes, Payette River, Idaho}, journal = {Geomorphology}, year = {2001}, volume = {37}, number = {1-2}, pages = {149--165} }
Hansen2001	Hansen, A.; Neilson, R.; Dale, V.; Flather, C.; Iverson, L.; Currie, D.; Shafer, S.; Cook, R. & Bartlein, P.	Global change in forests: Responses of species, communities, and biomes [BibTeX] [PDF]	2001	Bioscience Vol. 51 (9) , pp. 765-779	article	future vegetation changes
BibTeX: @article{Hansen2001, author = {Hansen, AJ and Neilson, RR and Dale, VH and Flather, CH and Iverson, LR and Currie, DJ and Shafer, S and Cook, R and Bartlein, PJ}, title = {Global change in forests: Responses of species, communities, and biomes}, journal = {Bioscience}, year = {2001}, volume = {51}, number = {9}, pages = {765--779} }
Harrison2003	Harrison, S.; Kutzbach, J.; Liu, Z.; Bartlein, P.; Otto-Bliesner, B.; Muhs, D.; Prentice, I. & Thompson, R.	Mid-Holocene climates of the Americas: a dynamical response to changed seasonality [Abstract] [BibTeX] [PDF]	2003	Climate Dynamics Vol. 20 (7-8) , pp. 663-688	article	paleoclimatic analysis and data-model comparisons
Abstract: Simulations of the climatic response to mid-Holocene (6 ka BP) orbital forcing with two coupled ocean-atmosphere models (FOAM and CSM) show enhancement of monsoonal precipitation in parts of the American Southwest. Central America and northernmost South America during Northern Hemisphere summer. The enhanced onshore flow that brings precipitation into Central America is caused by a northward displacement of the inter-tropical convergence zone, driven by cooling of the equatorial and warming of the northern subtropical and mid-latitude ocean. Ocean feedbacks also enhance precipitation over the American Southwest, although the increase in monsoon precipitation there is largely driven by increases in land-surface temperature. The northward shift in the equatorial precipitation band that causes enhanced precipitation in Central America and the American Southwest has a negative feedback effect on monsoonal precipitation in northern South America. The simulations demonstrate that mid-Holocene aridity in the mid-continent of North America is dynamically linked to the orbitally induced enhancement of the summer monsoon in the American Southwest, with a spatial structure (wet in the Southwest and dry in the mid-continent) similar to that found in strong monsoon years today. Changes in winter precipitation along the west coast of North America, in Central America and along the Gulf Coast, caused by southward-displacement of the westerly storm tracks, indicate that changes in the Northern Hemisphere winter monsoon also play a role in regional climate changes during the mid-Holocene. Although the simulations with FOAM and CSM differ in detail, the general mechanisms and patterns are common to both. The model results thus provide a coherent dynamical explanation for regional patterns of increased or decreased aridity shown by vegetation, lake status and aeolian data from the Americas.
BibTeX: @article{Harrison2003, author = {Harrison, SP and Kutzbach, JE and Liu, Z and Bartlein, PJ and Otto-Bliesner, B and Muhs, D and Prentice, IC and Thompson, RS}, title = {Mid-Holocene climates of the Americas: a dynamical response to changed seasonality}, journal = {Climate Dynamics}, year = {2003}, volume = {20}, number = {7-8}, pages = {663--688} }
Harrison1992	Harrison, S.; Prentice, I. & Bartlein, P.	Influence of insolation and glaciation on atmospheric circulation in the North Atlantic sector - implications of general-circulation model experiments for the late Quaternary climatology of Europe [Abstract] [BibTeX]	1992	Quaternary Science Reviews Vol. 11 (3) , pp. 283-299	article
Abstract: Atmospheric general circulation models have been used to simulate the sensitivity of regional climates to Late Quaternary changes in insolation, ice sheets and atmospheric CO2. Model results for full-glacial conditions (18 ka) show the Atlantic Westerly jet strengthened and shifted south, a corresponding southward shift of the Icelandic low and a strengthening and northward shift of the subtropical anticyclone (STA). A glacial anticyclone developed over the European ice sheet and cold, dry conditions prevailed over much of Europe. The full-glacial climate anomaly for the North Atlantic sector is explained by a combination of low atmospheric CO2 (reducing global surface temperatures) and circulation changes caused by the ice sheets. By the Early Holocene (9 ka) the ice sheets were much reduced while the orbital anomaly was near its maximum, producing midcontinental summer warming and winter cooling and a reduced latitudinal temperature gradient in the northern hemisphere in both seasons. The jet and the Icelandic low were displaced to north of their present position, producing strong onshore flow and mild, wet winters in northern Europe, while the STA was also shifted northwards, producing offshore flow and dry summers in the same region. During the late-glacial transition the effects of insolation and glaciation were antagonistic for some features of the circulation and synergistic for others. The model results suggest palaeoclimatic hypotheses that could be directly tested by comparison with palaeoclimatic data mapped at a synoptic scale.
BibTeX: @article{Harrison1992, author = {Harrison, SP and Prentice, IC and Bartlein, PJ}, title = {Influence of insolation and glaciation on atmospheric circulation in the North Atlantic sector - implications of general-circulation model experiments for the late Quaternary climatology of Europe}, journal = {Quaternary Science Reviews}, year = {1992}, volume = {11}, number = {3}, pages = {283--299} }
Higuera2010	Higuera, P.; Gavin, D.; Bartlein, P. & Hallett, D.	Peak detection in sediment-charcoal records: impacts of alternative data analysis methods on fire-history interpretations [Abstract] [BibTeX] [PDF]	2010	International Journal of Wildland Fire Vol. 19 (8) , pp. 996-1014	article
Abstract: Over the past several decades, high-resolution sediment-charcoal records have been increasingly used to reconstruct local fire history. Data analysis methods usually involve a decomposition that detrends a charcoal series and then applies a threshold value to isolate individual peaks, which are interpreted as fire episodes. Despite the proliferation of these studies, methods have evolved largely in the absence of a thorough statistical framework. We describe eight alternative decomposition models (four detrending methods used with two threshold-determination methods) and evaluate their sensitivity to a set of known parameters integrated into simulated charcoal records. Results indicate that the combination of a globally defined threshold with specific detrending methods can produce strongly biased results, depending on whether or not variance in a charcoal record is stationary through time. These biases are largely eliminated by using a locally defined threshold, which adapts to changes in variability throughout a charcoal record. Applying the alternative decomposition methods on three previously published charcoal records largely supports our conclusions from simulated records. We also present a minimum-count test for empirical records, which reduces the likelihood of false positives when charcoal counts are low. We conclude by discussing how to evaluate when peak detection methods are warranted with a given sediment-charcoal record.
BibTeX: @article{Higuera2010, author = {Higuera, PE and Gavin, DG and Bartlein, PJ and Hallett, DJ}, title = {Peak detection in sediment-charcoal records: impacts of alternative data analysis methods on fire-history interpretations}, journal = {International Journal of Wildland Fire}, year = {2010}, volume = {19}, number = {8}, pages = {996--1014} }
Higuera2007	Higuera, P.; Peters, M.; Brubaker, L. & Gavin, D.	Understanding the origin and analysis of sediment-charcoal records with a simulation model [Abstract] [BibTeX] [PDF]	2007	Quaternary Science Reviews Vol. 26 (13-14) , pp. 1790-1809	article
Abstract: Interpreting sediment-charcoal records is challenging because there is little information linking charcoal production from fires to charcoal accumulation in lakes. We present a numerical model simulating the major processes involved in this pathway. The model incorporates the size, location, and frequency of fires, primary and secondary charcoal transport, sediment mixing, and sediment sampling. We use the model as a tool to evaluate assumptions of charcoal dispersal and taphonomy and to assess the merits of inferring local and regional fire history by decomposing charcoal records into low-frequency ('background') and high-frequency ('peak') components. Under specific dispersal scenarios, the model generates records similar in appearance to sediment-charcoal records from Alaskan boreal forests. These scenarios require long-distance dispersal (e.g. 10(0)-10(1) km), consistent with observations from wildfires but longer than previously inferred from experimental dispersal data. More generally, charcoal accumulation in simulated records mainly reflects area burned within the charcoal source area. Variability in charcoal peak heights is primarily explained by the size of charcoal source areas relative to the size of simulated fires, with an increase in this ratio resulting in increased variability in peak heights. Mixing and multi-year sampling add noise to charcoal records, obscuring the relationship between area burned and charcoal accumulation. This noise highlights the need for statistical treatments of charcoal records. Using simulated records we demonstrate that long-term averages of charcoal accumulation (> 10 x mean fire return interval) correlate well with area burned within the entire charcoal source area. We further demonstrate how decomposing simulated records to isolate the peak component emphasizes fire occurrence at smaller spatial scales (< 1 km radius), despite the importance of long-distance charcoal dispersal in simulating charcoal records similar to observations. Together, these results provide theoretical support for the analysis of charcoal records using the decomposition approach. (C) 2007 Elsevier Ltd. All rights reserved.
BibTeX: @article{Higuera2007, author = {Higuera, PE and Peters, ME and Brubaker, LB and Gavin, DG}, title = {Understanding the origin and analysis of sediment-charcoal records with a simulation model}, journal = {Quaternary Science Reviews}, year = {2007}, volume = {26}, number = {13-14}, pages = {1790--1809} }
Hostetler1999a	Hostetler, S. & Bartlein, P. Webb, R.; Clark, P. & Kaigwin, L. (Hrsg.)	Simulation of the potential responses of regional climate and surface processes in western North America to a canonical Heinrich event ( Mechanisms of Global Climate Change at Millennial Time Scales ) [BibTeX] [PDF]	1999	Mechanisms of Global Climate Change at Millennial Time Scales , pp. 313-327	inbook
BibTeX: @inbook{Hostetler1999a, author = {Hostetler, SW and Bartlein, PJ}, title = {Mechanisms of Global Climate Change at Millennial Time Scales}, publisher = {American Geophysical Union}, year = {1999}, pages = {313-327} }
Hostetler1990	Hostetler, S. & Bartlein, P.	Simulation of lake evaporation with application to modeling lake level variations of Harney-Malheur Lake, Oregon [BibTeX]	1990	Water Resources Research Vol. 26 (10) , pp. 2603-2612	article
BibTeX: @article{Hostetler1990, author = {Hostetler, SW and Bartlein, PJ}, title = {Simulation of lake evaporation with application to modeling lake level variations of Harney-Malheur Lake, Oregon}, journal = {Water Resources Research}, year = {1990}, volume = {26}, number = {10}, pages = {2603--2612} }
Hostetler2000	Hostetler, S.; Bartlein, P.; Clark, P.; Small, E. & Solomon, A.	Simulated influences of Lake Agassiz on the climate of central North America 11,000 years ago [Abstract] [BibTeX] [Figures] [PDF]	2000	Nature Vol. 405 (6784) , pp. 334-337	article	http://geography.uoregon.edu/envchange/figures/hostetler-etal-nature-2000-figs/index.htmlb
Abstract: Eleven thousand years ago, large lakes existed in central and eastern North America along the margin of the Laurentide Ice Sheet. The large-scale North American climate at this time has been simulated with atmospheric general circulation models(1,2), but these relatively coarse global models do not resolve potentially important features of the mesoscale circulation that arise from interactions among the atmosphere, ice sheet, and proglacial lakes. Here we present simulations of the climate of central and eastern North America 11,000 years ago with a high-resolution, regional climate model nested within a general circulation model. The simulated climate is in general agreement with that inferred from palaeoecological evidence. Our experiments indicate that through mesoscale atmospheric feedbacks, the annual delivery of moisture to the Laurentide Ice Sheet was diminished at times of a large, cold Lake Agassiz relative to periods of lower lake stands. The resulting changes in the mass balance of the ice sheet may have contributed to fluctuations of the ice margin, thus affecting the routing of fresh water to the North Atlantic Ocean. A retreating ice margin during periods of high lake level may have opened an outlet for discharge of Lake Agassiz into the North Atlantic. A subsequent advance of the ice margin due to greater moisture delivery associated with a low lake level could have dammed the outlet, thereby reducing discharge to the North Atlantic. These variations may have been decisive in causing the Younger Dryas cold event(3,4).
BibTeX: @article{Hostetler2000, author = {Hostetler, SW and Bartlein, PJ and Clark, PU and Small, EE and Solomon, AM}, title = {Simulated influences of Lake Agassiz on the climate of central North America 11,000 years ago}, journal = {Nature}, year = {2000}, volume = {405}, number = {6784}, pages = {334--337}, note = {http://geography.uoregon.edu/envchange/figures/Hostetler-etal-Nature-2000-figs/index.html} }
Hostetler2003	Hostetler, S.; Bartlein, P.; Holman, J.; Shafer, S. & Solomon, A.	Using a regional climate model to diagnose climatological and meterological controls of wildfire in the western United States [BibTeX] [PDF]	2003	5th Symposium on Fire and Forest Meteorology. American Meteorological Society , pp. P1.3-1 - P1.3-5	inproceedings
BibTeX: @inproceedings{Hostetler2003, author = {Hostetler, SW and Bartlein, PJ and Holman, JO and Shafer, SL and Solomon, AM}, title = {Using a regional climate model to diagnose climatological and meterological controls of wildfire in the western United States}, booktitle = {5th Symposium on Fire and Forest Meteorology. American Meteorological Society}, year = {2003}, pages = {P1.3-1 - P1.3-5} }
Hostetler1999	Hostetler, S.; Clark, P.; Bartlein, P.; Mix, A. & Pisias, N.	Atmospheric transmission of North Atlantic Heinrich events [Abstract] [BibTeX] [Figures] [PDF]	1999	Journal of Geophysical Research-Atmospheres Vol. 104 (D4) , pp. 3947-3952	article	paleoclimatic analysis and data-model comparisons
Abstract: We model the response of the climate system during Heinrich event 2 (H2) by employing an atmospheric general circulation model, using boundary conditions based on the concept of a "canonical" Heinrich event. The canonical event is initialized with a full-height Laurentide ice sheet (LIS) and CLIMAP sea surface temperatures (SSTs), followed by lowering of the LIS, then warming of North Atlantic SSTs. Our modeled temperature and wind fields exhibit spatially variable responses over the Northern Hemisphere at each stage of the H2 event. In some regions the climatic responses are additive, whereas in other regions they cancel or are of opposite sign, suggesting that Heinrich event climatic variations may have left complex signatures in geologic records. We find variations in the tropical water balance and the mass balance of ice sheets, and implications for variations in terrestrial methane production from the contraction of northern permafrost regions and the expansion of tropical wetlands.
BibTeX: @article{Hostetler1999, author = {Hostetler, SW and Clark, PU and Bartlein, PJ and Mix, AC and Pisias, NJ}, title = {Atmospheric transmission of North Atlantic Heinrich events}, journal = {Journal of Geophysical Research-Atmospheres}, year = {1999}, volume = {104}, number = {D4}, pages = {3947--3952}, note = {http://geography.uoregon.edu/envchange/figures/Hostetler-etal-JGR-1999-figs/index.html} }
Hostetler1994	Hostetler, S.; Giorgi, F.; Bates, G. & BARTLEIN, P.	Lake-atmosphere feedbacks associated with paleolakes Bonneville and Lahontan [Abstract] [BibTeX]	1994	Science Vol. 263 (5147) , pp. 665-668	article
Abstract: A high-resolution, regional climate model nested within a general circulation model was used to study the interactions between the atmosphere and the large Pleistocene lakes in the Great Basin of the United States. Simulations for January and July 18,000 years ago indicate that moisture provided by synoptic-scale atmospheric circulation features was the primary component of the hydrologic budgets of Lakes Lahontan and Bonneville. In addition, lake-generated precipitation was a substantial component of the hydrologic budget of Lake Bonneville at that time. This local lake-atmosphere interaction may help explain differences in the relative sizes of these lakes 18,000 years ago.
BibTeX: @article{Hostetler1994, author = {Hostetler, SW and Giorgi, F and Bates, GT and BARTLEIN, PJ}, title = {Lake-atmosphere feedbacks associated with paleolakes Bonneville and Lahontan}, journal = {Science}, year = {1994}, volume = {263}, number = {5147}, pages = {665--668} }
Houlahan1992	Houlahan, J.; Marcus, W. & Shirmohammadi, A.	Estimating Maryland critical area acts impact on future nonpoint pollution along the Rhode River estuary [Abstract] [BibTeX] [PDF]	1992	Water Resources Bulletin Vol. 28 (3) , pp. 553-567	article
Abstract: This paper presents the results of an investigation of the effects of the Maryland Critical Area Act on generation of nonpoint source loads of phosphorus, nitrogen, and sediment to the Rhode River estuary. The Simple Method model, the Marcus and Kearney regression model, and the CREAMS model were used to estimate annual loads under: (1) present conditions, (2) maximum land use development allowable under the Act, and (3) two sets of future land use conditions that might occur if the Act were not in place. Results indicate that the Critical Area Act can reduce the present generation of nonpoint nutrient and sediment loadings 20-30 percent from the regulated area. These reductions can occur while preserving agricultural lands and allowing limited residential and urban development. The decrease in nutrient loadings is primarily dependent upon implementation and enforcement of agricultural best management practices (BMPs). The BMPs could reduce present agricultural nutrient loadings by 90 percent to a level comparable to loadings from residential areas. The estimated effectiveness of the Critical Area Act is even greater when compared to potential future nutrient loadings if development in the area remains unregulated. Unrestricted residential and urban development could increase nutrient loadings by 200 percent to 1000 percent as compared to controlled development under Critical Area Act guidelines.The Critical Area Act primarily prevents these future increases by severely limiting woodland cutting, with lesser results obtained by requiring urban BMPs.
BibTeX: @article{Houlahan1992, author = {Houlahan, J and Marcus, WA and Shirmohammadi, A}, title = {Estimating Maryland critical area acts impact on future nonpoint pollution along the Rhode River estuary}, journal = {Water Resources Bulletin}, year = {1992}, volume = {28}, number = {3}, pages = {553--567} }
Hughes2006	Hughes, M.; McDowell, P. & Marcus, W.	Accuracy assessment of georectified aerial photographs: Implications for measuring lateral channel movement in a GIS [Abstract] [BibTeX] [PDF]	2006	Geomorphology Vol. 74 (1-4) , pp. 1-16	article	fluvial geomorphology
Abstract: Aerial photographs are commonly used to measure planform river channel change. We investigated the sources and implications of georectification error in the measurement of lateral channel movement by testing how the number (6-30) and type (human versus natural landscape features) of ground-control points (GCPs) and the order of the transformation polynomial (first-, second-, and third-order) affected the spatial accuracy of a typical georectified aerial photograph. Error was assessed using the root-mean-square error (RMSE) of the GCPs as well as error in 31 independent test points. The RMSE and the mean and median values of test-point errors were relatively insensitive to the number of GCPs above eight, but the upper range of test-point errors showed marked improvement (i.e., the number of extreme errors was reduced) as more GCPS were used for georectification. Using more GCPs thus improved overall georectification accuracy, but this improvement was not indicated by the RMSE, suggesting that independent test-points located in key areas of interest should be used in addition to RSME to evaluate georectification error. The order of the transformation polynomial also influenced test-point accuracy; the second-order polynomial function yielded the best result for the terrain of the study area. GCP type exerted a less consistent influence on test-point accuracy, suggesting that although hard-edged points (e.g., roof comers) are favored as GCPs, some soft-edged points (e.g., trees) may be used without adding significant error. Based upon these results, we believe that aerial photos of a floodplain landscape similar to that of our study can be consistently georectified to an accuracy of approximately +/- 5 m, with similar to 10% chance of greater error. The implications of georectification error for measuring lateral channel movement are demonstrated with a multiple buffer analysis, which documents the inverse relationship between the size of the buffers applied to two channel centerlines and the magnitude of change detected between them. This study demonstrates the importance of using an independent test-point analysis in addition to the RSME to evaluate and treat locational error in channel change studies. (c) 2005 Published by Elsevier B.V.
BibTeX: @article{Hughes2006, author = {Hughes, ML and McDowell, PF and Marcus, WA}, title = {Accuracy assessment of georectified aerial photographs: Implications for measuring lateral channel movement in a GIS}, journal = {Geomorphology}, year = {2006}, volume = {74}, number = {1-4}, pages = {1--16} }
Huntley1989	Huntley, B.; Bartlein, P. & PRENTICE, I.	Climatic control of the distribution and abundance of beech (Fagus L) in Europe and North America [BibTeX] [PDF]	1989	Journal of Biogeography Vol. 16 (6) , pp. 551-560	article	vegetation and climate
BibTeX: @article{Huntley1989, author = {Huntley, B and Bartlein, PJ and PRENTICE, IC}, title = {Climatic control of the distribution and abundance of beech (Fagus L) in Europe and North America}, journal = {Journal of Biogeography}, year = {1989}, volume = {16}, number = {6}, pages = {551--560} }
Huntley2004	Huntley, B.; Green, R.; Collingham, Y.; Hill, J.; Willis, S.; Bartlein, P.; Cramer, W.; Hagemeijer, W. & Thomas, C.	The performance of models relating species geographical distributions to climate is independent of trophic level [Abstract] [BibTeX] [PDF]	2004	Ecology Letters Vol. 7 (5) , pp. 417-426	article	vegetation and climate
Abstract: Species - climate 'envelope' models are widely used to evaluate potential climate change impacts upon species and biodiversity. Previous studies have used a variety of methods to fit models making it difficult to assess relative model performance for different taxonomic groups, life forms or trophic levels. Here we use the same climatic data and modelling approach for 306 European species representing three major taxa ( higher plants, insects and birds), and including species of different life form and from four trophic levels. Goodness-of-fit measures showed that useful models were fitted for > 96% of species, and that model performance was related neither to major taxonomic group nor to trophic level. These results confirm that such climate envelope models provide the best approach currently available for evaluating reliably the potential impacts of future climate change upon biodiversity.
BibTeX: @article{Huntley2004, author = {Huntley, B and Green, RE and Collingham, YC and Hill, JK and Willis, SG and Bartlein, PJ and Cramer, W and Hagemeijer, WJM and Thomas, CJ}, title = {The performance of models relating species geographical distributions to climate is independent of trophic level}, journal = {Ecology Letters}, year = {2004}, volume = {7}, number = {5}, pages = {417--426} }
Jacquez2002	Jacquez, G.; Marcus, W.; Aspinall, R. & Greiling, D.	Exposure assessment using high spatial resolution hyperspectral (HSRH) imagery [BibTeX] [PDF]	2002	Journal of Geographical Systems Vol. 4 , pp. 1-14	article	remote sensing
BibTeX: @article{Jacquez2002, author = {Jacquez, GM and Marcus, WA and Aspinall, RJ and Greiling, D}, title = {Exposure assessment using high spatial resolution hyperspectral (HSRH) imagery}, journal = {Journal of Geographical Systems}, year = {2002}, volume = {4}, pages = {1-14} }
James2006	James, L. & Marcus, W.	The 2006 Binghamton Geomorphology Symposium on The Human Role in Changing Fluvial Systems - Preface [BibTeX] [PDF]	2006	Geomorphology Vol. 79 (3-4) , pp. 144-147	article	fluvial geomorphology
BibTeX: @article{James2006, author = {James, LA and Marcus, WA}, title = {The 2006 Binghamton Geomorphology Symposium on The Human Role in Changing Fluvial Systems - Preface}, journal = {Geomorphology}, year = {2006}, volume = {79}, number = {3-4}, pages = {144--147} }
James2006a	James, L. & Marcus, W.	The human role in changing fluvial systems: Retrospect, inventory and prospect [Abstract] [BibTeX]	2006	Geomorphology Vol. 79 (3-4) , pp. 152-171	article
Abstract: Historical and modern scientific contexts are provided for the 2006 Binghamton Geomorphology Symposium on the Human Role in Changing Fluvial Systems. The 2006 symposium provides a synthesis of research concerned with human impacts on fluvial systems - including hydrologic and geomorphic changes to watersheds - while also commemorating the 50th anniversary of the 1955 Man's Role in Changing the Face of the Earth Symposium [Thomas, Jr., W. L. (Ed.), 1956a. Man's Role in Changing the Face of the Earth. Univ. Chicago Press, Chicago. 1193 pp]. This paper examines the 1955 symposium from the perspective of human impacts on rivers, reviews current inquiry on anthropogenic interactions in fluvial systems, and anticipates future directions in this field. Although the 1955 symposium did not have an explicit geomorphic focus, it set the stage for many subsequent anthropogeomorphic studies. The 1955 conference provided guidance to geomorphologists by recommending and practicing interdisciplinary scholarship, through the use of diverse methodologies applied at extensive temporal and geographical scales, and through its insistence on an integrated understanding of human interactions with nature. Since 1956, research on human impacts to fluvial systems has been influenced by fundamental changes in why the research is done, what is studied, how river studies are conducted, and who does the research. Rationales for river research are now driven to a greater degree by institutional needs, environmental regulations, and aquatic restoration. New techniques include a host of dating, spatial imaging, and ground measurement methods that can be coupled with analytical functions and digital models. These new methods have led to a greater understanding of channel change, variations across multiple temporal and spatial scales, and integrated watershed perspectives; all changes that are reflected by the papers in this volume. These new methods also bring a set of technical demands for the training of geomorphologists. The 2006 Binghamton Geomorphology Symposium complements the 1956 symposium by providing a more specific and updated view of river systems coupled with human interactions. The symposium focuses on linkages between human land use, structures, and channel modification with geomorphology, hydrology, and ecology. The emergence of sustainability as a central policy guideline in environmental management should generate greater interest in geomorphic perspectives, especially as they pertain to human activities. The lack of theories of anthropogeomorphic change, however, presents a challenge for the next generation of geomorphologists in this rapidly growing subfield. (c) 2006 Elsevier B.V. All rights reserved.
BibTeX: @article{James2006a, author = {James, LA and Marcus, WA}, title = {The human role in changing fluvial systems: Retrospect, inventory and prospect}, journal = {Geomorphology}, year = {2006}, volume = {79}, number = {3-4}, pages = {152--171} }
Joussaume1999	Joussaume, S.; Taylor, K.; Braconnot, P.; Mitchell, J.; Kutzbach, J.; Harrison, S.; Prentice, I.; Broccoli, A.; Abe-Ouchi, A.; Bartlein, P.; Bonfils, C.; Dong, B.; Guiot, J.; Herterich, K.; Hewitt, C.; Jolly, D.; Kim, J.; Kislov, A.; Kitoh, A.; Loutre, M.; Masson, V.; McAvaney, B.; McFarlane, N.; de Noblet, N.; Peltier, W.; Peterschmitt, J.; Pollard, D.; Rind, D.; Royer, J.; Schlesinger, M.; Syktus, J.; Thompson, S.; Valdes, P.; Vettoretti, G.; Webb, R. & Wyputta, U.	Monsoon changes for 6000 years ago: Results of 18 simulations from the Paleoclimate Modeling Intercomparison Project (PMIP) [Abstract] [BibTeX]	1999	Geophysical Research Letters Vol. 26 (7) , pp. 859-862	article	paleoclimatology
Abstract: Amplification of the northern hemisphere seasonal cycle of insolation during the mid-Holocene causes a northward shift of the main regions of monsoon precipitation over Africa and India in all 18 simulations conducted for the Paleoclimate Modeling Intercomparison Project (PMIP). Differences among simulations are related to differences in model formulation. Despite qualitative agreement with paleoecological estimates of biome shifts, the magnitude of the monsoon increases over northern Africa are underestimated by all the models.
BibTeX: @article{Joussaume1999, author = {Joussaume, S and Taylor, KE and Braconnot, P and Mitchell, JFB and Kutzbach, JE and Harrison, SP and Prentice, IC and Broccoli, AJ and Abe-Ouchi, A and Bartlein, PJ and Bonfils, C and Dong, B and Guiot, J and Herterich, K and Hewitt, CD and Jolly, D and Kim, JW and Kislov, A and Kitoh, A and Loutre, MF and Masson, V and McAvaney, B and McFarlane, N and de Noblet, N and Peltier, WR and Peterschmitt, JY and Pollard, D and Rind, D and Royer, JF and Schlesinger, ME and Syktus, J and Thompson, S and Valdes, P and Vettoretti, G and Webb, RS and Wyputta, U}, title = {Monsoon changes for 6000 years ago: Results of 18 simulations from the Paleoclimate Modeling Intercomparison Project (PMIP)}, journal = {Geophysical Research Letters}, year = {1999}, volume = {26}, number = {7}, pages = {859--862} }
Kaplan2003	Kaplan, J.; Bigelow, N.; Prentice, I.; Harrison, S.; Bartlein, P.; Christensen, T.; Cramer, W.; Matveyeva, N.; McGuire, A.; Murray, D.; Razzhivin, V.; Smith, B.; Walker, D.; Anderson, P.; Andreev, A.; Brubaker, L.; Edwards, M. & Lozhkin, A.	Climate change and Arctic ecosystems: 2. Modeling, paleodata-model comparisons, and future projections [Abstract] [BibTeX] [PDF]	2003	Journal of Geophysical Research-Atmospheres Vol. 108 (D19) , pp. -	article	vegetation and climate
Abstract: [1] Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55degreesN, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry-biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid-Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low- and high-shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid-Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid-Holocene and present. Simulated physiological effects of the CO2 increase (to >700 ppm) at high latitudes were slight compared with the effects of the change in climate.
BibTeX: @article{Kaplan2003, author = {Kaplan, JO and Bigelow, NH and Prentice, IC and Harrison, SP and Bartlein, PJ and Christensen, TR and Cramer, W and Matveyeva, NV and McGuire, AD and Murray, DF and Razzhivin, VY and Smith, B and Walker, DA and Anderson, PM and Andreev, AA and Brubaker, LB and Edwards, ME and Lozhkin, AV}, title = {Climate change and Arctic ecosystems: 2. Modeling, paleodata-model comparisons, and future projections}, journal = {Journal of Geophysical Research-Atmospheres}, year = {2003}, volume = {108}, number = {D19}, pages = {--} }
Kaufman2004	Kaufman, D.; Ager, T.; Anderson, N.; Anderson, P.; Andrews, J.; Bartlein, P.; Brubaker, L.; Coats, L.; Cwynar, L.; Duvall, M.; Dyke, A.; Edwards, M.; Eisner, W.; Gajewski, K.; Geirsdottir, A.; Hu, F.; Jennings, A.; Kaplan, M.; Kerwin, M.; Lozhkin, A.; MacDonald, G.; Miller, G.; Mock, C.; Oswald, W.; Otto-Bliesner, B.; Porinchu, D.; Ruhland, K.; Smol, J.; Steig, E. & Wolfe, B.	Holocene thermal maximum in the western Arctic (0-180 degrees W) [Abstract] [BibTeX] [PDF]	2004	Quaternary Science Reviews Vol. 23 (5-6) , pp. 529-560	article
Abstract: The spatio-temporal pattern of peak Holocene warmth (Holocene thermal maximum, HTM) is traced over 140 sites across the Western Hemisphere of the Arctic (0-180degreesW; north of similar to60degreesN). Paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer-than-present conditions at 120 of these sites. At the 16 terrestrial sites where quantitative estimates have been obtained, local HTM temperatures (primarily summer estimates) were on average 1.6+/-0.8degreesC higher than present (approximate average of the 20th century), but the warming was time-transgressive across the western Arctic. As the precession-driven summer insolation anomaly peaked 12-10ka (thousands of calendar years ago), warming was concentrated in northwest North America, while cool conditions lingered in the northeast. Alaska and northwest Canada experienced the HTM between ca 11 and 9 ka, about 4000 yr prior to the HTM in northeast Canada. The delayed warming in Quebec and Labrador was linked to the residual Laurentide Ice Sheet, which chilled the region through its impact on surface energy balance and ocean circulation. The lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change. The spatial asymmetry of warming during the HTM resembles the pattern of warming observed in the Arctic over the last several decades. Although the two warmings are described at different temporal scales, and the HTM was additionally affected by the residual Laurentide ice, the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing. Unlike the HTM, however, future warming will not be counterbalanced by the cooling effect of a residual North American ice sheet. (C) 2003 Elsevier Ltd. All rights reserved.
BibTeX: @article{Kaufman2004, author = {Kaufman, DS and Ager, TA and Anderson, NJ and Anderson, PM and Andrews, JT and Bartlein, PJ and Brubaker, LB and Coats, LL and Cwynar, LC and Duvall, ML and Dyke, AS and Edwards, ME and Eisner, WR and Gajewski, K and Geirsdottir, A and Hu, FS and Jennings, AE and Kaplan, MR and Kerwin, MN and Lozhkin, AV and MacDonald, GM and Miller, GH and Mock, CJ and Oswald, WW and Otto-Bliesner, BL and Porinchu, DF and Ruhland, K and Smol, JP and Steig, EJ and Wolfe, BB}, title = {Holocene thermal maximum in the western Arctic (0-180 degrees W)}, journal = {Quaternary Science Reviews}, year = {2004}, volume = {23}, number = {5-6}, pages = {529--560} }
Kutzbach1996	Kutzbach, J.; Bartlein, P.; Foley, J.; Harrison, S.; Hostetler, S.; Liu, Z.; Prentice, I. & Webb, T.	Potential role of vegetation feedback in the climate sensitivity of high-latitude regions: A case study at 6000 years BP [Abstract] [BibTeX]	1996	Global Biogeochemical Cycles Vol. 10 (4) , pp. 727-736	article
Abstract: Previous climate model simulations have shown that the configuration of the Earth's orbit during the early to mid-Holocene (approximately 10-5 kyr) can account for the generally warmer-than-present conditions experienced by the high latitudes of the northern hemisphere. New simulations for 6 kyr with two atmospheric/mixed-layer ocean models (Community Climate Model, version 1, CCM1, and Global ENvironmental and Ecological Simulation of Interactive Systems, version 2, GENESIS 2) are presented here and compared with results from two previous simulations with GENESIS 1 that were obtained with and without the albedo feedback due to climate-induced poleward expansion of the boreal forest. The climate model results are summarized in the form of potential vegetation maps obtained with the global BIOME model, which facilitates visual comparisons both among models and with pollen and plant macrofossil data recording shifts of the forest-tundra boundary. A preliminary synthesis shows that the forest limit was shifted 100-200 km north in most sectors. Both CCM1 and GENESIS 2 produced a shift of this magnitude. GENESIS 1 however produced too small a shift, except when the boreal forest albedo feedback was included. The feedback in this case was estimated to have amplified forest expansion by approximately 50%. The forest limit changes also show meridional patterns (greatest expansion in central Siberia and little or none in Alaska and Labrador) which have yet to be reproduced by models. Further progress in understanding of the processes involved in the response of climate and vegetation to orbital forcing will require both the deployment of coupled atmosphere-biosphere-ocean models and the development df more comprehensive observational data sets.
BibTeX: @article{Kutzbach1996, author = {Kutzbach, JE and Bartlein, PJ and Foley, JA and Harrison, SP and Hostetler, SW and Liu, Z and Prentice, IC and Webb, T}, title = {Potential role of vegetation feedback in the climate sensitivity of high-latitude regions: A case study at 6000 years BP}, journal = {Global Biogeochemical Cycles}, year = {1996}, volume = {10}, number = {4}, pages = {727--736} }
Ladd1998	Ladd, S.; Marcus, W. & Cherry, S.	Differences in trace metal concentrations among fluvial morphologic units and implications for sampling [Abstract] [BibTeX] [PDF]	1998	Environmental Geology Vol. 36 (3-4) , pp. 259-270	article
Abstract: This study examines the segregation of trace metals within and between fluvial morphologic units in sand-sized and finer bed sediments a cobble bed stream. The types of fluvial morphologic units sampled are low gradient riffles, high gradient riffles, glides, eddy drop zones, lateral scour pools, attached bars, and detached bars. Three to nine samples were collected from ten of each type of morphologic unit. All 12 metals show significantly different concentrations between some morphologic units in sediments smaller than 2 mm. Eddy drop zones and attached bars consistently have the highest metal concentrations, while low gradient riffles, high gradient riffles, and glides typically have the lowest concentrations. Metals showing the greatest between-unit variability are Al, Cr, Fe, Cu, and Ti, followed by Co, Mn, and Pb, while Mg, Mn, V, and Zn display relatively few differences between units. Lateral and longitudinal variations of metals within units are not significant, and there was no consistent, predictable variation in metal concentrations with distance downstream. Results indicate that metal studies in other gravel- and cobble-bed streams should include a reconnaissance survey to determine variations between morphologic units, stratify sampling by morphologic unit, and analyze spatial autocorrelation to determine sample spacing.
BibTeX: @article{Ladd1998, author = {Ladd, SC and Marcus, WA and Cherry, S}, title = {Differences in trace metal concentrations among fluvial morphologic units and implications for sampling}, journal = {Environmental Geology}, year = {1998}, volume = {36}, number = {3-4}, pages = {259--270} }
Lawler2009	Lawler, J.; Shafer, S.; White, D.; Kareiva, P.; Maurer, E.; Blaustein, A. & Bartlein, P.	Projected climate-induced faunal change in the Western Hemisphere [Abstract] [BibTeX]	2009	Ecology Vol. 90 (3) , pp. 588-597	article	future climate and vegetation change
Abstract: Climate change is predicted to be one of the greatest drivers of ecological change in the coming century. Increases in temperature over the last century have clearly been linked to shifts in species distributions. Given the magnitude of projected future climatic changes, we can expect even larger range shifts in the coming century. These changes will, in turn, alter ecological communities and the functioning of ecosystems. Despite the seriousness of predicted climate change, the uncertainty in climate-change projections makes it difficult for conservation managers and planners to proactively respond to climate stresses. To address one aspect of this uncertainty, we identified predictions of faunal change for which a high level of consensus was exhibited by different climate models. Specifically, we assessed the potential effects of 30 coupled atmosphere-ocean general circulation model (AOGCM) future-climate simulations on the geographic ranges of 2954 species of birds, mammals, and amphibians in the Western Hemisphere. Eighty percent of the climate projections based on a relatively low greenhouse-gas emissions scenario result in the local loss of at least 10% of the vertebrate fauna over much of North and South America. The largest changes in fauna are predicted for the tundra, Central America, and the Andes Mountains where, assuming no dispersal constraints, specific areas are likely to experience over 90% turnover, so that faunal distributions in the future will bear little resemblance to those of today.
BibTeX: @article{Lawler2009, author = {Lawler, JJ and Shafer, SL and White, D and Kareiva, P and Maurer, EP and Blaustein, AR and Bartlein, PJ}, title = {Projected climate-induced faunal change in the Western Hemisphere}, journal = {Ecology}, year = {2009}, volume = {90}, number = {3}, pages = {588--597} }
Legleiter2003	Legleiter, C.; Lawrence, R.; Fonstad, M.; Marcus, W. & Aspinall, R.	Fluvial response a decade after wildfire in the northern Yellowstone ecosystem: a spatially explicit analysis [Abstract] [BibTeX] [PDF]	2003	Geomorphology Vol. 54 (3-4) , pp. 119-136	article	fluvial geomorphology
Abstract: Forest fire is a vital ecological process capable of inducing complex fluvial response, but the integration of these effects across entire watersheds remains poorly understood. We collected downstream cross-sectional and geomorphic data, acquired geographic information on land cover and forest fire, and performed spatially explicit statistical analyses to examine fire-related impacts in catchments burned to varying degrees. Generalized least squares (GLS) regression models suggested that channels with a greater percentage of burned drainage area were associated with markedly higher cross-sectional stream power, relatively smaller width/depth ratios, and lower bank failure rates 12 to 13 years after the fires. These results implied that streams became more powerful in the aftermath of forest fire and that net incision had been the primary response in second- to fourth-order channels since the 1988 Yellowstone fires. The extensive geographic coverage of our data, spanning multiple basins with measurements spaced every 100 m, allowed us to hypothesize a process-response model based on these results. We suggest that a wave of fire-related sediment propagates through burned catchments. High runoff events or even moderate flows provide sufficient energy to evacuate the finer-grained material delivered from burned hillslopes to the channel network over a period of 5-10 years. The combination of elevated post-fire discharges and decreased sediment supply then induces an episode of incision. Site-specific channel changes are highly variable because streams can accommodate post-fire increases in energy and sediment supply through multiple modes of adjustment. Characterizing the spatial distribution of stream power would provide a valuable management tool because this variable is strongly associated with percent-burned drainage area and integrates several elements of complex fluvial response. Future research focused on the channel substrate and its evolution through time is needed, but our results indicate a fundamental linkage between fire and fluvial processes. (C) 2002 Elsevier Science B.V. All rights reserved.
BibTeX: @article{Legleiter2003, author = {Legleiter, CJ and Lawrence, RL and Fonstad, MA and Marcus, WA and Aspinall, R}, title = {Fluvial response a decade after wildfire in the northern Yellowstone ecosystem: a spatially explicit analysis}, journal = {Geomorphology}, year = {2003}, volume = {54}, number = {3-4}, pages = {119--136} }
Legleiter2002	Legleiter, C.; Marcus, W. & Lawrence, R.	Effects of sensor resolution on mapping in-stream habitats [Abstract] [BibTeX]	2002	Photogrammetric Engineering and Remote Sensing Vol. 68 (8) , pp. 801-807	article
Abstract: Effects of spatial, spectral, and radiometric resolution on remote mapping of fourth-order in-stream habitats were evaluated by comparing hyperspectral imagery to simulated multispectral data. Spectral resolution was more important than spatial or radiometric resolution in improving classification accuracies, although overall accuracies never exceeded 62 percent. Overall accuracies were significantly greater for (1) hyperspectral data (7.2 percent) compared to simulated multispectral imagery, (2) 1-m pixels (4.7 percent) compared to 2.5-m pixels, and (3) 11-bit data (0.8 percent) compared to 8-bit data. Higher spatial resolution also enabled removal of transitional areas between units by using interior buffers, improving accuracy by up to 15.6 percent. We believe low overall accuracies were primarily due to the subjective and oversimplified nature of the polygon-bused field maps used as ground reference data, and high-resolution imagery might provide a more detailed representation of in-stream habitats. Improved methods of collecting ground reference data, utilizing a point-based approach, should be developed for assessing the accuracy of classifications derived from fine spatial resolution (less than 5-m) imagery.
BibTeX: @article{Legleiter2002, author = {Legleiter, CJ and Marcus, WA and Lawrence, RL}, title = {Effects of sensor resolution on mapping in-stream habitats}, journal = {Photogrammetric Engineering and Remote Sensing}, year = {2002}, volume = {68}, number = {8}, pages = {801--807} }
Legleiter2004	Legleiter, C.; Roberts, D.; Marcus, W. & Fonstad, M.	Passive optical remote sensing of river channel morphology and in-stream habitat: Physical basis and feasibility [Abstract] [BibTeX] [PDF]	2004	Remote Sensing of Environment Vol. 93 (4) , pp. 493-510	article
Abstract: Successful monitoring of ecologically significant, vulnerable fluvial systems will require improved quantitative techniques for mapping channel morphology and in-stream habitat. In this study, we assess the ability of remote sensing to contribute to these objectives by (1) describing the underlying radiative transfer processes, drawing upon research conducted in shallow marine environments; (2) modeling the effects of water depth, substrate type, suspended sediment concentration, and surface turbulence; (3) quantifying the limitations imposed by finite detector sensitivity and linear quantization; and (4) evaluating two depth retrieval algorithms using simulated and field-measured spectra and archival imagery. The degree to which variations in depth and substrate can be resolved depends on bottom albedo and water column optical properties, and scattering by suspended sediment obscures substrate spectral features and reduces the resolution of depth estimates. Converting continuous radiance signals to discrete digital numbers implies that depth estimates take the form of contour intervals that become wider as depth increases and as bottom albedo and detector sensitivity decrease. Our results indicate that a simple band ratio can provide an image-derived variable that is strongly linearly related to water depth across a broad range of stream conditions. This technique outperformed the linear transform method used in previous stream studies, most notably for upwelling radiance spectra [R-2=0.79 for the ln(560 nm/690 nm) ratio]. Applied to uncalibrated multispectral and hyperspectral images of a fourth-order stream in Yellowstone National Park, this flexible technique produced hydraulically reasonable maps of relative depth. Although radiometric precision and spatial resolution will impose fundamental limitations in practice, remote mapping of channel morphology and in-stream habitat is feasible and can become a powerful tool for scientists and managers. (C) 2004 Elsevier Inc. All rights reserved.
BibTeX: @article{Legleiter2004, author = {Legleiter, CJ and Roberts, DA and Marcus, WA and Fonstad, MA}, title = {Passive optical remote sensing of river channel morphology and in-stream habitat: Physical basis and feasibility}, journal = {Remote Sensing of Environment}, year = {2004}, volume = {93}, number = {4}, pages = {493--510} }
Lertzman2002	Lertzman, K.; Gavin, D.; Hallett, D.; Brubaker, L.; Lepofsky, D. & Mathewes, R.	Long-term fire regime estimated from soil charcoal in coastal temperate rainforests [Abstract] [BibTeX] [PDF]	2002	Conservation Ecology Vol. 6 (2) , pp. -	article
Abstract: Coastal temperate rainforests from southeast Alaska through to southern Oregon are ecologically distinct from forests of neighboring regions, which have a drier, or more continental, climate and disturbance regimes dominated by fires. The long-term role of fire remains one of the key outstanding sources of uncertainty in the historical dynamics of the wetter and less seasonal forests that dominate the northerly two thirds of the rainforest region in British Columbia and Alaska. Here, we describe the long-term fire regime in two forests on the south coast of British Columbia by means of 244 AMS radiocarbon dates of charcoal buried in forest soils. In both forests, some sites have experienced no fire over the last 6000 years and many other sites have experienced only one or two fires during that time. Intervals between fires vary from a few centuries to several thousand years. In contrast to other conifer forests, this supports a model of forest dynamics where fires are of minor ecological importance. Instead, forest history is dominated by fine-scale processes of disturbance and recovery that maintain an ubiquitous late-successional character over the forest landscape. This has significant implications for ecosystem-based forest management and our understanding of carbon storage in forest soils.
BibTeX: @article{Lertzman2002, author = {Lertzman, K and Gavin, D and Hallett, D and Brubaker, L and Lepofsky, D and Mathewes, R}, title = {Long-term fire regime estimated from soil charcoal in coastal temperate rainforests}, journal = {Conservation Ecology}, year = {2002}, volume = {6}, number = {2}, pages = {--} }
Light2004	Light, A. & Bartlein, P.	The end of the rainbow? Color schemes for improved data graphics [BibTeX] [PDF]	2004	Eos Vol. 85 , pp. 385,391	article	scientific visualization
BibTeX: @article{Light2004, author = {Light, A and Bartlein, PJ}, title = {The end of the rainbow? Color schemes for improved data graphics}, journal = {Eos}, year = {2004}, volume = {85}, pages = {385,391} }
Long2011	Long, C.; Power, M. & Bartlein, P.	The effects of fire and tephra deposition on forest vegetation in the Central Cascades, Oregon [Abstract] [BibTeX] [PDF]	2011	Quaternary Research Vol. 75 (1) , pp. 151-158	article
Abstract: High-resolution charcoal and pollen analyses were used to reconstruct a 12,000-yr-long fire and vegetation history of the Tumalo Lake watershed and to examine the short-term effects that tephra deposition have on forest composition and fire regime. The record suggests that, from 12,000 to 9200 cal yr BP, the watershed was dominated by an open Pinus forest with Artemisia as a common understory species. Fire episodes occurred on average every 115 yr. Beginning around 9200 cal yr BP, and continuing to the present. Abies became more common while Artemisia declined, suggesting the development of a closed forest structure and a decrease in the frequency of fire episodes, occurring on average every 160 yr. High-resolution pollen analyses before and after the emplacement of three distinct tephra deposits in the watershed suggest that nonarboreal species were most affected by tephra events and that recovery of the vegetation community to previous conditions took between 40 and 100 yr. Changes in forest composition were not associated with tephra depositional events or changes in fire-episode frequency, implying that the regional climate is the more important control on long-term forest composition and structure of the vegetation in the Cascade Range. (C) 2010 University of Washington. Published by Elsevier Inc. All rights reserved.
BibTeX: @article{Long2011, author = {Long, CJ and Power, MJ and Bartlein, PJ}, title = {The effects of fire and tephra deposition on forest vegetation in the Central Cascades, Oregon}, journal = {Quaternary Research}, year = {2011}, volume = {75}, number = {1}, pages = {151--158} }
Long2007	Long, C.; Whitlock, C. & Bartlein, P.	Holocene vegetation and fire history of the Coast Range, western Oregon, USA [Abstract] [BibTeX] [PDF]	2007	Holocene Vol. 17 (7) , pp. 917-926	article
Abstract: Pollen and high-resolution charcoal records from three lakes were examined to reconstruct the vegetation and fire history of the Oregon Coast Range for the last 9000 years. The sites are located along a north-to-south effective precipitation gradient and changes in vegetation and fire activity provided information on the nature of this gradient in the past. The relation of vegetation to climate change was examined at millennial timescales and the relation between fire and climate was examined on centennial timescales by comparing fire-interval distribution and fire synchrony between sites. The pollen data indicate more fire-adapted vegetation during the early-Holocene period (c. 9000 to 6700 cal. yr BP), followed by a shift to forests with more fire-sensitive taxa in the mid Holocene (c. 6700 cal. yr BP to 2700 cal. yr BP) and modern forest assemblages developing over the last c. 2700 years. Comparisons of fire-interval distributions showed that the time between fires was similar between two of the three combinations of sites, suggesting that the moisture gradient has played an important role in determining long-term fire frequency. However, century-scale synchrony of fire occurrence between the two sites with the largest difference in effective precipitation suggests that centennial-scale shifts in climate may have overcome the environmental differences between these locations. Asynchrony in fire occurrence between the sites with more similar effective precipitation implies that local conditions may have played an important role in determining fire synchrony between sites with similar long-term climate histories.
BibTeX: @article{Long2007, author = {Long, CJ and Whitlock, C and Bartlein, PJ}, title = {Holocene vegetation and fire history of the Coast Range, western Oregon, USA}, journal = {Holocene}, year = {2007}, volume = {17}, number = {7}, pages = {917--926} }
Long1998	Long, C.; Whitlock, C.; Bartlein, P. & Millspaugh, S.	A 9000-year fire history from the Oregon Coast Range, based on a high-resolution charcoal study [Abstract] [BibTeX] [Figures] [PDF]	1998	Canadian Journal of Forest Research Vol. 28 (5) , pp. 774-787	article	fire: paleo and modern
Abstract: High-resolution analysis of macroscopic charcoal in sediment cores from Little Lake was used to reconstruct the fire history of the last 9000 years. Variations in sediment magnetism were examined to detect changes in allochthonous sedimentation associated with past fire occurrence. Fire intervals from ca. 9000 to 6850 calendar years BP averaged 110 +/- 20 years, when the climate was warmer and drier than today and xerophytic vegetation dominated. From ca. 6850 to 2750 calendar years BP the mean fire interval lengthened to 160 +/- 20 years in conjunction with the onset of cool humid conditions. Fire-sensitive species, such as Thuja plicata Donn ex D. Don, Tsuga heterophylla (Raf.) Sarg., and Picea sitchensis (Bong.) Carr., increased in abundance. At ca. 4000 calendar years BP, increases in allochthonous sedimentation increased the delivery of secondary charcoal to the site. From ca. 2750 calendar years BP to present, the mean fire interval increased to 230 +/- 30 years as cool humid conditions and mesophytic taxa prevailed. The Little Lake record suggests that fire frequency has varied continuously on millennial time scales as a result of climate change and the present-day fire regime has been present for no more than 1000 years.
BibTeX: @article{Long1998, author = {Long, CJ and Whitlock, C and Bartlein, PJ and Millspaugh, SH}, title = {A 9000-year fire history from the Oregon Coast Range, based on a high-resolution charcoal study}, journal = {Canadian Journal of Forest Research}, year = {1998}, volume = {28}, number = {5}, pages = {774--787}, note = {http://geography.uoregon.edu/envchange/figures/Long-etal-CJFR-1998-figs/index.html} }
Lynch2003	Lynch, A.; Rivers, A. & Bartlein, P.	An assessment of the influence of land cover uncertainties on the simulation of global climate in the early Holocene [Abstract] [BibTeX] [PDF]	2003	Climate Dynamics Vol. 21 (3-4) , pp. 243-256	article	paleoclimatic analysis and data-model comparisons
Abstract: Six and 21 kyear BP represent the extreme states of climate since the last glacial maximum. The early Holocene, in contrast, was a time of transition, experiencing rapidly melting continental ice sheets, rising sea-level, and increasing summer insolation. Key features of the climate, illustrated by an NCAR CCM3 general circulation model experiment representing 11 kyr BP, include enhanced continentality and seasonality, and an enhanced northern monsoon. The principal circulation responses to the 11 kyr BP boundary conditions can be summarized as an intensification and northward shift of the mean meridional circulation and an intensification of the planetary wave structure of the Northern Hemisphere in northern summer, and a slight intensification of the mean meridional circulation coupled with a southward shift in the planetary wave structure in northern winter. These changes are manifest in the enhancement of the typical seasonal cycle of sea-level pressure in the Northern Hemisphere relative to that of the present day, and enhancement and equatorward shift of the Aleutian and Icelandic lows in northern winter. Over the period 15-8 kyr BP, within the current boreal forest zone, herbaceous tundra was replaced by shrub tundra, and subsequently by evergreen or deciduous forest, but there is uncertainty in the location, timing, and exact nature of these transitions. The specific location of the relatively small area of the Asian boreal forest-tundra transition can have an impact on regional climate, primarily in the net shortwave radiation component of the surface energy budget in spring, and in the cloudiness, net shortwave radiation, and turbulent heat fluxes in summer. These changes also have an impact on global climate. Our results suggest that the additional northern heating leads to a reduced equator-pole heat transport in the Northern Hemisphere which then influences heat and momentum transport in the Southern Hemisphere.
BibTeX: @article{Lynch2003, author = {Lynch, AH and Rivers, AR and Bartlein, PJ}, title = {An assessment of the influence of land cover uncertainties on the simulation of global climate in the early Holocene}, journal = {Climate Dynamics}, year = {2003}, volume = {21}, number = {3-4}, pages = {243--256} }
Magilligan1997	Magilligan, F. & McDowell, P.	Stream channel adjustments following elimination of cattle grazing [Abstract] [BibTeX]	1997	Journal of the American Water Resources Association Vol. 33 (4) , pp. 867-878	article
Abstract: Cattle grazing practices in the western United States have contributed to widespread riparian degradation resulting in unstable channel morphologies and the loss of fish habitat. Because of prolonged disturbance, numerous riparian areas oil both public and private lands have been fenced to exclude cattle in order to promote vegetation establishment and riparian improvement. We selected four gravel-bedded, steep alluvial streams in eastern Oregon with cattle exclosures greater than 14 years old for an analysis of geomorphic adjustments following the removal of cattle grazing. We compare channels inside exclosures and in adjacent grazed reaches to identify the salient stream channel properties that respond to the removal of riparian stresses and to document the magnitude of these changes. Results indicate that significant changes occur, with reductions in bankfull dimensions and increases in pool area being the most common and identifiable changes. At all four sites, bankfull widths are narrower by 10 to 20 percent, and the percentage of channel area occupied by pools is higher in the exclosure by 8 to 15 percent. The increase in pool area is primarily offset by a reduction in the percent glide area. Not all of the channel properties demonstrate adjustment, indicating that perhaps 14 years is an insufficient duration for these variables to adjust.
BibTeX: @article{Magilligan1997, author = {Magilligan, FJ and McDowell, PF}, title = {Stream channel adjustments following elimination of cattle grazing}, journal = {Journal of the American Water Resources Association}, year = {1997}, volume = {33}, number = {4}, pages = {867--878} }
Marcus1996a	Marcus, M. & Marcus, W.	Barry C. Bishop - In memoriam [BibTeX]	1996	Mountain Research and Development Vol. 16 (3) , pp. 188-192	article
BibTeX: @article{Marcus1996a, author = {Marcus, MG and Marcus, WA}, title = {Barry C. Bishop - In memoriam}, journal = {Mountain Research and Development}, year = {1996}, volume = {16}, number = {3}, pages = {188--192} }
Marcus2002a	Marcus, W.	Mapping of stream microhabitats with high spatial resolution hyperspectral imagery [BibTeX] [PDF]	2002	Journal of Geographical Systems Vol. 4 , pp. 113-126	article	remote sensing
BibTeX: @article{Marcus2002a, author = {Marcus, WA}, title = {Mapping of stream microhabitats with high spatial resolution hyperspectral imagery}, journal = {Journal of Geographical Systems}, year = {2002}, volume = {4}, pages = {113-126} }
Marcus1996b	Marcus, W.	Segment-scale patterns and hydraulics of trace metal concentrations in fine grain sediments of a cobble and boulder bed mountain stream, southeast Alaska [Abstract] [BibTeX]	1996	Mountain Research and Development Vol. 16 (3) , pp. 211-220	article
Abstract: This study documents and analyzes spatial patterns of variability in 12 trace metals in sand-size and finer sediments over a 2 km segment of a boulder and cobble bed mountain stream. The analysis focuses on concentrations rather than the total metal mass budget, because it is typically variations in metal concentrations that are important for assessing potential environmental impacts. There are no consistent downstream variations in metal concentrations, which indicates that there are no significant geochemical changes or external sources of metals in the study segment. In fact, much of the spatial variability within the stream segment appears to be random, although a dimensionless shear stress model predicts the majority of locations where peak concentrations of metals contained in heavy minerals occur. The dimensionless shear stress model, however, only predicts the potential for enrichment and many sites where potential enrichment is predicted contain low concentrations of metals. Peak concentrations do not appear to be associated with metal-rich sediment waves moving through the system, but instead are probably the result of local hydraulic variability. Sampling of boulder and cobble streams should be stratified by hydraulic environments in order to capture the full range of minimum and maximum metal concentrations within the stream system.
BibTeX: @article{Marcus1996b, author = {Marcus, WA}, title = {Segment-scale patterns and hydraulics of trace metal concentrations in fine grain sediments of a cobble and boulder bed mountain stream, southeast Alaska}, journal = {Mountain Research and Development}, year = {1996}, volume = {16}, number = {3}, pages = {211--220} }
Marcus1989	Marcus, W.	Dilution mixing estimates of trace-metal concentrations in suspended sediments [BibTeX]	1989	Environmental Geology and Water Sciences Vol. 14 (3) , pp. 213-219	article
BibTeX: @article{Marcus1989, author = {Marcus, WA}, title = {Dilution mixing estimates of trace-metal concentrations in suspended sediments}, journal = {Environmental Geology and Water Sciences}, year = {1989}, volume = {14}, number = {3}, pages = {213--219} }
Marcus1989a	Marcus, W.	Lag-time routing of suspended sediment concentrations during unsteady-flow [BibTeX]	1989	Geological Society of America Bulletin Vol. 101 (5) , pp. 644-651	article
BibTeX: @article{Marcus1989a, author = {Marcus, WA}, title = {Lag-time routing of suspended sediment concentrations during unsteady-flow}, journal = {Geological Society of America Bulletin}, year = {1989}, volume = {101}, number = {5}, pages = {644--651} }
Marcus1989b	Marcus, W.	Regulating contaminated sediments in aquatic environments - a hydrologic perspective [BibTeX]	1989	Environmental Management Vol. 13 (6) , pp. 703-713	article
BibTeX: @article{Marcus1989b, author = {Marcus, WA}, title = {Regulating contaminated sediments in aquatic environments - a hydrologic perspective}, journal = {Environmental Management}, year = {1989}, volume = {13}, number = {6}, pages = {703--713} }
Marcus1987	Marcus, W.	Copper dispersion in ephemeral stream sediments [BibTeX]	1987	Earth Surface Processes and Landforms Vol. 12 (3) , pp. 217-228	article
BibTeX: @article{Marcus1987, author = {Marcus, WA}, title = {Copper dispersion in ephemeral stream sediments}, journal = {Earth Surface Processes and Landforms}, year = {1987}, volume = {12}, number = {3}, pages = {217--228} }
Marcus2010	Marcus, W. & Fonstad, M.	Remote sensing of rivers: the emergence of a subdiscipline in the river sciences [Abstract] [BibTeX]	2010	Earth Surface Processes and Landforms Vol. 35 (15) , pp. 1867-1872	article
Abstract: This article reports on the special issue of Earth Surface Processes and Landforms dedicated to remote sensing of rivers. This emerging subdiscipline of river science has grown at a rapid rate in recent years because of: (a) the growing desire and need for data to document and explore the full range of spatial and temporal variations in river systems; (b) evolving technologies that enable lower cost data acquisition, processing and analysis at reach to catchment to continental scales; and (c) the increasing engagement of river scientists with GIScience. The convergence of these factors and the ever growing number of practitioners speaks to the need for more communication among researchers, a major reason for creating this special issue. The 12 articles in the volume cover a broad spectrum of applications that use a variety of platforms and sensors, ranging from photogrammetric mapping of riffle-pool morphology beneath forest canopy using a camera mounted on a hand held pole to satellite-based synthetic radar mapping of subcontinental scale hydrology of large rivers. In this overview each of the 12 articles is briefly summarized. Based on these works and other research, it is concluded that the time for more widespread application of river remote sensing techniques is now. To promote more widespread use of remote sensing techniques for river science and management, the following are advocated: (a) developing stand alone or plug-in software products that enable non-expert users to implement these new methods, (b) incorporating remote sensing of rivers training into classes, workshops, and on-line tutorials; and (c) promoting more intentional and formal collaboration among members of the river remote sensing community. Copyright (c) 2010 John Wiley & Sons, Ltd.
BibTeX: @article{Marcus2010, author = {Marcus, WA and Fonstad, MA}, title = {Remote sensing of rivers: the emergence of a subdiscipline in the river sciences}, journal = {Earth Surface Processes and Landforms}, year = {2010}, volume = {35}, number = {15}, pages = {1867--1872} }
Marcus2008	Marcus, W. & Fonstad, M.	Optical remote mapping of rivers at sub-meter resolutions and watershed extents [Abstract] [BibTeX] [PDF]	2008	Earth Surface Processes and Landforms Vol. 33 (1) , pp. 4-24	article
Abstract: At watershed extents, our understanding of river form, process and function is largely based on locally intensive mapping of river reaches, or on spatially extensive but low density data scattered throughout a watershed (e.g. cross sections). The net effect has been to characterize streams as discontinuous systems. Recent advances in optical remote sensing of rivers indicate that it should now be possible to generate accurate and continuous maps of in-stream habitats, depths, algae, wood, stream power and other features at sub-meter resolutions across entire watersheds so long as the water is clear and the aerial view is unobstructed. Such maps would transform river science and management by providing improved data, better models and explanation, and enhanced applications. Obstacles to achieving this vision include variations in optics associated with shadows, water clarity, variable substrates and target-sun angle geometry. Logistical obstacles are primarily due to the reliance of existing ground validation procedures on time-of-flight field measurements, which are impossible to accomplish at watershed extents, particularly in large and difficult to access river basins. Philosophical issues must also be addressed that relate to the expectations around accuracy assessment, the need for and utility of physically based models to evaluate remote sensing results and the ethics of revealing information about river resources at fine spatial resolutions. Despite these obstacles and issues, catchment extent remote river mapping is now feasible, as is demonstrated by a proof-of-concept example for the Nueces River, Texas, and examples of how different image types (radar, lidar, thermal) could be merged with optical imagery. The greatest obstacle to development and implementation of more remote sensing, catchment scale 'river observatories' is the absence of broadly based funding initiatives to support collaborative research by multiple investigators in different river settings. Copyright (c) 2007 John Wiley & Sons, Ltd.
BibTeX: @article{Marcus2008, author = {Marcus, WA and Fonstad, MA}, title = {Optical remote mapping of rivers at sub-meter resolutions and watershed extents}, journal = {Earth Surface Processes and Landforms}, year = {2008}, volume = {33}, number = {1}, pages = {4--24} }
Marcus1991	Marcus, W. & Kearney, M.	Upland and coastal sediment sources in a Chesapeake Bay estuary [BibTeX] [PDF]	1991	Annals of the Association of American Geographers Vol. 81 (3) , pp. 408-424	article
BibTeX: @article{Marcus1991, author = {Marcus, WA and Kearney, MS}, title = {Upland and coastal sediment sources in a Chesapeake Bay estuary}, journal = {Annals of the Association of American Geographers}, year = {1991}, volume = {81}, number = {3}, pages = {408--424} }
Marcus1995	Marcus, W.; Ladd, S. & Stoughton, J.	Pebble counts and the role of user-dependent bias in documenting sediment size distributions [Abstract] [BibTeX]	1995	Water Resources Research Vol. 31 (10) , pp. 2625-2631	article
Abstract: Replicate subaqueous pebble counts show that measurement and selection bias can significantly affect sediment size distribution data. The standard deviation about replicate means increases linearly with sediment size and is independent of the sediment percentile (e.g., d(50), d(84), etc.). For samples collected by one person, sampling error varies from 2 +/- 2.6 mm to 300 +/- 35.4 mm within one standard deviation. For samples collected by different individuals, sampling bias increases the error from 2 +/- 4.2 mm to 300 +/- 63.8 mm. Whenever possible, only one individual should select and measure pebbles, which improves the ability of the pebble count to delineate trends between sites or over time (although the absolute size values may be in error due to bias). Bias can be reduced by rigorous training of individuals, by using templates to measure sediment size, and by using grids on the stream bottom to select particles. If two or more individuals collect samples, they should conduct replicate samples to provide a basis for later calibration of results.
BibTeX: @article{Marcus1995, author = {Marcus, WA and Ladd, SC and Stoughton, JA}, title = {Pebble counts and the role of user-dependent bias in documenting sediment size distributions}, journal = {Water Resources Research}, year = {1995}, volume = {31}, number = {10}, pages = {2625--2631} }
Marcus2003	Marcus, W.; Legleiter, C.; Aspinall, R.; Boardman, J. & Crabtree, R.	High spatial resolution hyperspectral mapping of in-stream habitats, depths, and woody debris in mountain streams [Abstract] [BibTeX] [PDF]	2003	Geomorphology Vol. 55 (1-4) , pp. 363-380	article
Abstract: This article evaluates the potential of I-m resolution, 128-band hyperspectral imagery for mapping in-stream habitats, depths, and woody debris in third- to fifth-order streams in the northern Yellowstone region. Maximum likelihood supervised classification using principal component images provided overall classification accuracies for in-stream habitats (glides, riffles, pools, and eddy drop zones) ranging from 69% for third-order streams to 86% for fifth-order streams. This scale dependency of classification accuracy was probably driven by the greater proportion of transitional boundary areas in the smaller streams. Multiple regressions of measured depths (y) versus principal component scores (x(1), x(2),..., x(n)) generated R-2 values ranging from 67% for high-gradient riffles to 99% for glides in a fifth-order reach. R 2 values were lower in third-order reaches, ranging from 28% for runs and glides to 94% for pools. The less accurate depth estimates obtained for smaller streams probably resulted from the relative increase in the number of mixed pixels, where a wide range of depths and surface turbulence occurred within a single pixel. Matched filter (MF) mapping of woody debris generated overall accuracies of 83% in the fifth-order Lamar River. Accuracy figures for the in-stream habitat and wood mapping may have been misleadingly low because the fine-resolution imagery captured fine-scale variations not mapped by field teams, which in turn generated false "misclassifications" when the image and field maps were compared. The use of high spatial resolution hyperspectral (HSRH) imagery for stream mapping is limited by the need for clear water to measure depth, by any tree cover obscuring the stream, and by the limited availability of airborne hyperspectral sensors. Nonetheless, the high accuracies achieved in northern Yellowstone streams indicate that HSRH imagery can be a powerful tool for watershed-wide mapping, monitoring, and modeling of streams. (C) 2003 Elsevier Science B.V. All rights reserved.
BibTeX: @article{Marcus2003, author = {Marcus, WA and Legleiter, CJ and Aspinall, RJ and Boardman, JW and Crabtree, RL}, title = {High spatial resolution hyperspectral mapping of in-stream habitats, depths, and woody debris in mountain streams}, journal = {Geomorphology}, year = {2003}, volume = {55}, number = {1-4}, pages = {363--380} }
Marcus1996	Marcus, W. & Marcus, M.	Geographer, explorer, friend: The worlds of Barry C. Bishop, 1932-1994 [BibTeX]	1996	Mountain Research and Development Vol. 16 (3) , pp. 193-198	article
BibTeX: @article{Marcus1996, author = {Marcus, WA and Marcus, MG}, title = {Geographer, explorer, friend: The worlds of Barry C. Bishop, 1932-1994}, journal = {Mountain Research and Development}, year = {1996}, volume = {16}, number = {3}, pages = {193--198} }
Marcus2002	Marcus, W.; Marston, R.; Colvard, C. & Gray, R.	Mapping the spatial and temporal distributions of woody debris in streams of the Greater Yellowstone Ecosystem, USA [Abstract] [BibTeX] [PDF]	2002	Geomorphology Vol. 44 (3-4) , pp. 323-335	article
Abstract: The objectives of this study were: (1) to document spatial and temporal distributions of large woody debris (LWD) at watershed scales and investigate some of the controlling processes; and (2) to judge the potential for mapping LWD accumulations with airborne multispectral imagery. Field surveys were conducted on the Snake River, Soda Butte Creek, and Cache Creek in the Greater Yellowstone Ecosystem, USA. The amount of woody debris per kilometer is highest in 2nd order streams, widely variable in 3rd and 4th order streams, and relatively low in the 6th order system. Floods led to increases in woody debris in 2nd order streams, Floods redistributed the wood in 3rd and 4th order streams, removing it from the channel and stranding it on bars, but appeared to generate little change in the total amount of wood throughout the channel system. The movement of woody debris suggests a system that is the reverse of most sediment transport systems in mountains. In 1st and 2nd order tributaries, the wood is too large to be moved and the system is transport-limited, with floods introducing new material through undercutting, but not removing wood through downstream transport. In the intermediate 3rd and 4th order channels, the system displays characteristics of dynamic equilibrium, where the channel is able remove the debris at approximately the same rate that it is introduced. The spatial distribution and quantity of wood in 3rd and 4th order reaches varies widely, however, as wood is alternatively stranded on gravel bars or moved downstream during periods of bar mobilization. In the 6th order and larger channels, the system becomes supply-limited, where almost all material in the main stream can be transported out of the central channel by normal stream flows and deposition occurs primarily on banks or in eddy pool environments. Attempts to map woody debris with 1-m resolution digital four-band imagery were generally unsuccessful, primarily because the imagery could not distinguish the narrow logs within a pixel from the surrounding sand and gravel background and due to problems in precisely coregistering imagery and field maps. (C) 2002 Elsevier Science B.V. All rights reserved.
BibTeX: @article{Marcus2002, author = {Marcus, WA and Marston, RA and Colvard, CR and Gray, RD}, title = {Mapping the spatial and temporal distributions of woody debris in streams of the Greater Yellowstone Ecosystem, USA}, journal = {Geomorphology}, year = {2002}, volume = {44}, number = {3-4}, pages = {323--335} }
Marcus2007a	Marcus, W.; Meacham, J.; Rodman, A. & Steingisser, A.	Visual Fields: Atlas of Yellowstone � preliminary work [BibTeX] [PDF]	2007	Cartographic Perspectives Vol. 57 , pp. 86-87	article
BibTeX: @article{Marcus2007a, author = {Marcus, WA and Meacham, JE and Rodman, A and Steingisser, A}, title = {Visual Fields: Atlas of Yellowstone � preliminary work}, journal = {Cartographic Perspectives}, year = {2007}, volume = {57}, pages = {86-87} }
Marcus2001	Marcus, W.; Meyer, G. & Nimmo, D.	Geomorphic control of persistent mine impacts in a Yellowstone Park stream and implications for the recovery of fluvial systems [Abstract] [BibTeX] [PDF]	2001	Geology Vol. 29 (4) , pp. 355-358	article
Abstract: A half-century after mine closure, metal contamination from sulfide ore mining in the headwaters continues to impair riparian vegetation and aquatic macroinvertebrates along Soda Butte Creek, Yellowstone National Park. A tailings dam failure in 1950 emplaced metal-rich sediment at high flood-plain levels, above 50 yr to 100 yr flood stages in 1996 and 1997. These large natural floods removed only a small part of the contaminated sediment through bank erosion; they also failed to lower in-channel Cu concentrations, because increased erosion of mine waste during high hows balances increased inputs of uncontaminated sediments, generating no net change in concentrations. Geomorphic processes controlling movement of contaminated sediments indicate that mine impacts will persist for centuries in Soda Butte Creek and imply long-lasting impacts in similarly affected streams worldwide.
BibTeX: @article{Marcus2001, author = {Marcus, WA and Meyer, GA and Nimmo, DR}, title = {Geomorphic control of persistent mine impacts in a Yellowstone Park stream and implications for the recovery of fluvial systems}, journal = {Geology}, year = {2001}, volume = {29}, number = {4}, pages = {355--358} }
Marcus1998	Marcus, W.; Milner, G. & Maxwell, B.	Spotted knapweed distribution in stock camps and trails of the Selway-Bitterroot Wilderness [Abstract] [BibTeX]	1998	Great Basin Naturalist Vol. 58 (2) , pp. 156-166	article
Abstract: This article documents spotted knapweed (Centaurea maculosa Lam.) in 30 campsites and along 5 trails in the Selway-Bitterroot Wilderness and assesses the role of disturbance and environmental factors in controlling infestation. Spotted knapweed was present in only 6 of 30 surveyed campsites and limited portions of all 5 trails that were sampled. All spotted knapweed in camps was below 1700 m elevation, in open canopy, and in areas with an opportunity class disturbance ranking of 3 or 4. Overall disturbance levels measured using U.S. Forest Service Site Impact Worksheets (SIWs) did not help predict occurrence of spotted knapweed, although bare mineral soil, vegetation loss, and development variables of SIWs provide some explanation of spotted knapweed presence or absence. There was no significant difference in knapweed frequency between areas used predominantly by horses and those used by humans within camps. Over 95% of spotted knapweed along trails was found within 0.5 km of the trailhead, occurred within 4.6 m of the trail, and had low reproductive potential. If the Bitterroot portion of the Selway-Bitterroot Wilderness is representative of forested wilderness areas in the Northern Rockies, then the perceived threat of spotted knapweed to wilderness areas may substantially exceed the actual danger in many instances. Study findings indicate that managers should conduct surveys before initiating costly control measures in wilderness areas, that eradication may be a viable alternative when spotted knapweed numbers are this low, and that regulations promoting minimum-impact camping should reduce spotted knapweed infestation.
BibTeX: @article{Marcus1998, author = {Marcus, WA and Milner, G and Maxwell, B}, title = {Spotted knapweed distribution in stock camps and trails of the Selway-Bitterroot Wilderness}, journal = {Great Basin Naturalist}, year = {1998}, volume = {58}, number = {2}, pages = {156--166} }
Marcus1993	Marcus, W.; Nielsen, C. & Cornwell, J.	Sediment budget-based estimates of trace-metal inputs to a Chesapeake estuary [Abstract] [BibTeX] [PDF]	1993	Environmental Geology Vol. 22 (1) , pp. 1-9	article	fluvial systems pollution
Abstract: This article evaluates whether a sediment budget for the South River, Maryland, can be coupled with metals data from sediment cores to identify and quantify sources of historic metal inputs to marsh and subtidal sediments along the estuary. Metal inputs to estuarine marsh sediments come from fluvial runoff and atmospheric deposition. Metal inputs to subtidal sediments come from atmospheric deposition, fluvial runoff, coastal erosion, and estuarine waters. The metals budget for the estuary indicates that metal inputs from coastal erosion have remained relatively constant since 1840. Historical variations in metal contents of marsh sediments have probably resulted primarily from increasing atmospheric deposition in this century. but prior to 1900 may reflect changing fluvial sources, atmospheric inputs, or factors not quantified by the budget. Residual Pb, Cu, and Zn in the marsh sediments not accounted for by fluvial inputs was low to moderate in 1840, decreased to near zero circa 1910, and by 1987 had increased to levels that were one to ten times greater than those of 1840. Sources of variability in subtidal cores could not be clearly discerned because of geochemical fluxes, turbulent mixing, and bioturbation within the cores. The sediment-metal budgeting approach appears to be a viable method for delineating metal sources in small, relatively simple estuarine systems like the South River and in systems where recent deposition (for example, prograding marshes) prevents use of deep core analysis to identify ''background'' levels of metal. In larger systems or systems with more variable sources of sediment and metal input, however, assumptions and measurement errors in the metal budgeting approach suggest that deep core analysis and normalization techniques are probably preferable for identifying anthropogenic impacts.
BibTeX: @article{Marcus1993, author = {Marcus, WA and Nielsen, CC and Cornwell, JC}, title = {Sediment budget-based estimates of trace-metal inputs to a Chesapeake estuary}, journal = {Environmental Geology}, year = {1993}, volume = {22}, number = {1}, pages = {1--9} }
Marcus2011	Marcus, W.; Rasmussen, J. & Fonstad, M.	Response of the fluvial wood system to fire and floods in northern Yellowstone [Abstract] [BibTeX]	2011	Annals of the Association of American Geographers Vol. 101 (1) , pp. 21-44	article	fluvial geomorphology
Abstract: We map the distribution of wood continuously along 73.4 km of second- through fifth-order streams in Yellowstone National Park and develop a Monte Carlo model of wood supply, transport, and storage to investigate: (1) spatial distributions of wood in burned and unburned basins, (2) associations between geomorphology and spatial distributions of wood, and (3) effects of flood timing and sequence on wood distributions. Wood counts in 2000 and 2001 vary by over two orders of magnitude over distances of several hundred meters. Qualitative models using catchment-scale characterizations of streams (e.g., whether a stream is third or fourth order) do not explain the degree of local variability. Reach-scale wood counts are weakly related to channel width in the extensively burned Cache Creek basin and to streamside forest cover and number of channel threads in all basins. Wood counts are not related to other reach-scale variations in channel morphology or fire effects. Monte Carlo simulations indicate that postfire flood timing and sequence drive variability in wood counts, with spatial variations in dominant processes and asynchronous timing of fire and floods creating a complex cascade of disturbance and a patchwork mosaic of wood. Existing descriptive models for postfire wood response do not predict this mosaic, although they capture the central tendency of variations. The central tendency is, however, a poor predictor of postdisturbance wood accumulations, so we develop a probabilistic model that better captures the range of potential postfire responses. We make recommendations for wood monitoring and management based on the empirical data and model results.
BibTeX: @article{Marcus2011, author = {Marcus, WA and Rasmussen, J and Fonstad, MA}, title = {Response of the fluvial wood system to fire and floods in northern Yellowstone}, journal = {Annals of the Association of American Geographers}, year = {2011}, volume = {101}, number = {1}, pages = {21--44} }
Marcus1992	Marcus, W.; Roberts, K.; Harvey, L. & Tackman, G.	An evaluation of methods for estimating Mannings-n in small mountain streams [Abstract] [BibTeX]	1992	Mountain Research and Development Vol. 12 (3) , pp. 227-239	article	fluvial geomorphology
Abstract: This article evaluates eleven techniques for estimating Manning's roughness coefficient in a small mountain stream (hydraulic radius less than 0.25 m). Observed roughness values at 15 sites were very high compared to lower gradient streams, ranging from 0.056 to 0.183. Jarrett's (1984) technique produced the best estimates of Manning's n, although it overestimated roughness by an average of 32% in the steep, turbulent flow. The other ten estimation methods significantly under predicted Manning's n, often by an order of magnitude. The underestimates occur because the methods do not adequately address the effects on flow resistance of large sediment sizes, low ratios of flow depth to hydraulic radius, steep slopes, and severe turbulence. In addition, observers using subjective visual estimation techniques underestimated roughness because of their training in lowland settings. The poor performance of the estimation techniques suggests that discharge should be measured directly whenever possible in steep mountain streams, particularly when determining discharges at low flows where a significant portion of the bed sediments are near to or are breaking the water surface. If one must use roughness estimates to calculate discharge in a small mountain stream, then the Jarrett (1984) method provides the most reasonable estimates of resistance to flow, although care should be taken to avoid reaches with plunge pool sequences and hydraulic jumps.
BibTeX: @article{Marcus1992, author = {Marcus, WA and Roberts, K and Harvey, L and Tackman, G}, title = {An evaluation of methods for estimating Mannings-n in small mountain streams}, journal = {Mountain Research and Development}, year = {1992}, volume = {12}, number = {3}, pages = {227--239} }
Marlon2008	Marlon, J.; Bartlein, P.; Carcaillet, C.; Gavin, D.; Harrison, S.; Higuera, P.; Joos, F.; Power, M. & Prentice, I.	Climate and human influences on global biomass burning over the past two millennia [Abstract] [BibTeX] [PDF]	2008	Nature Geoscience Vol. 1 (10) , pp. 697-702	article
Abstract: Large, well-documented wildfires have recently generated worldwide attention, and raised concerns about the impacts of humans and climate change on wildfire regimes. However, comparatively little is known about the patterns and driving forces of global fire activity before the twentieth century. Here we compile sedimentary charcoal records spanning six continents to document trends in both natural and anthropogenic biomass burning for the past two millennia. We find that global biomass burning declined from AD 1 to similar to 1750, before rising sharply between 1750 and 1870. Global burning then declined abruptly after 1870. The early decline in biomass burning occurred in concert with a global cooling trend and despite a rise in the human population. We suggest the subsequent rise was linked to increasing human influences, such as population growth and land-use changes. Our compilation suggests that the final decline occurred despite increasing air temperatures and population. We attribute this reduction in the amount of biomass burned over the past 150 years to the global expansion of intensive grazing, agriculture and fire management.
BibTeX: @article{Marlon2008, author = {Marlon, JR and Bartlein, PJ and Carcaillet, C and Gavin, DG and Harrison, SP and Higuera, PE and Joos, F and Power, MJ and Prentice, IC}, title = {Climate and human influences on global biomass burning over the past two millennia}, journal = {Nature Geoscience}, year = {2008}, volume = {1}, number = {10}, pages = {697--702} }
Marlon2009	Marlon, J.; Bartlein, P.; Walsh, M.; Harrison, S.; Brown, K.; Edwards, M.; Higuera, P.; Power, M.; Anderson, R.; Briles, C.; Brunelle, A.; Carcaillet, C.; Daniels, M.; Hu, F.; Lavoie, M.; Long, C.; Minckley, T.; Richard, P.; Scott, A.; Shafer, D.; Tinner, W.; Umbanhowar, C. & Whitlock, C.	Wildfire responses to abrupt climate change in North America [Abstract] [BibTeX]	2009	Proceedings of the National Academy Of Sciences of the United States of the USA Vol. 106 (8) , pp. 2519-2524	article
Abstract: It is widely accepted, based on data from the last few decades and on model simulations, that anthropogenic climate change will cause increased fire activity. However, less attention has been paid to the relationship between abrupt climate changes and heightened fire activity in the paleorecord. We use 35 charcoal and pollen records to assess how fire regimes in North America changed during the last glacial-interglacial transition ( 15 to 10 ka), a time of large and rapid climate changes. We also test the hypothesis that a comet impact initiated continental-scale wildfires at 12.9 ka; the data do not support this idea, nor are continent-wide fires indicated at any time during deglaciation. There are, however, clear links between large climate changes and fire activity. Biomass burning gradually increased from the glacial period to the beginning of the Younger Dryas. Although there are changes in biomass burning during the Younger Dryas, there is no systematic trend. There is a further increase in biomass burning after the Younger Dryas. Intervals of rapid climate change at 13.9, 13.2, and 11.7 ka are marked by large increases in fire activity. The timing of changes in fire is not coincident with changes in human population density or the timing of the extinction of the megafauna. Although these factors could have contributed to fire-regime changes at individual sites or at specific times, the charcoal data indicate an important role for climate, and particularly rapid climate change, in determining broad-scale levels of fire activity.
BibTeX: @article{Marlon2009, author = {Marlon, JR and Bartlein, PJ and Walsh, MK and Harrison, SP and Brown, KJ and Edwards, ME and Higuera, PE and Power, MJ and Anderson, RS and Briles, C and Brunelle, A and Carcaillet, C and Daniels, M and Hu, FS and Lavoie, M and Long, C and Minckley, T and Richard, PJH and Scott, AC and Shafer, DS and Tinner, W and Umbanhowar, CE and Whitlock, C}, title = {Wildfire responses to abrupt climate change in North America}, journal = {Proceedings of the National Academy Of Sciences of the United States of the USA}, year = {2009}, volume = {106}, number = {8}, pages = {2519--2524} }
Marlon2006	Marlon, J.; Bartlein, P. & Whitlock, C.	Fire-fuel-climate linkages in the northwestern USA during the Holocene [Abstract] [BibTeX]	2006	Holocene Vol. 16 (8) , pp. 1059-1071	article
Abstract: Variations in fire regimes can be inferred from changes in the abundance of sedimentary charcoal found in lake and bog sediments. When analysed with pollen data, inferences can be made about past vegetation dynamics and climate as well. The analysis of high-resolution charcoal records generally involves the decomposition of charcoal influx into (a) a slowly varying 'background' component that provides information about long-term changes in regional fire activity, biomass and/or depositional processes, and (b) a 'peaks' component that represents local fire events. In this study, 15 high-resolution charcoal records from the northwestern USA and associated pollen data were examined to describe the variations and controls of charcoal influx and background trends. Late-Holocene charcoal influx levels at each site were compared with late-Holocene sedimentation rates, vegetation and fire frequency, and with modern climate and physical site characteristics to better understand the spatial variability in charcoal abundance. Charcoal abundance was largely determined by physical site characteristics (eg, lake and watershed size) and the proportion of woody taxa. Background trends displayed regional similarities, - closely with woody taxa proportions in and the subcontinental scale trend based on all records correlated the pollen spectra. Background charcoal and woody taxa proportions increased together from minima in the Late Glacial to maxima in the late Holocene. The strong similarity in these trends suggests that background charcoal influx is a function of fuel characteristics, which in turn are governed by climate and vegetation. Variations in sedimentation rate and fire frequency had little influence on background charcoal trends.
BibTeX: @article{Marlon2006, author = {Marlon, J and Bartlein, PJ and Whitlock, C}, title = {Fire-fuel-climate linkages in the northwestern USA during the Holocene}, journal = {Holocene}, year = {2006}, volume = {16}, number = {8}, pages = {1059--1071} }
McCarty1998	McCarty, D.; Moore, J. & Marcus, W.	Mineralogy and trace element association in an acid mine drainage iron oxide precipitate; comparison of selective extractions [Abstract] [BibTeX]	1998	Applied Geochemistry Vol. 13 (2) , pp. 165-176	article
Abstract: Mineral and trace element characterization of an Fe-rich precipitate from an acid mine system was accomplished by X-ray diffraction (XRD), differential X-ray diffraction, and ICP chemical analysis. A primary objective was to evaluate the effectiveness of common selective dissolution treatments in determining the association of minerals with potentially toxic trace elements; The precipitate consisted primarily of goethite, a poorly crystalline phase resembling synthetic ferrihydrite, dolomite and gypsum in clay-size fractions. The ammonium oxalate and EDTA treatments, which are thought by some workers to dissolve only poorly crystalline phases, were found to dissolve a significant amount of crystalline goethite. However, the oxalate extraction did dissolve more ferrihydrite than the other treatments tested. A solution of 0.1 M hydroxylamine hydrochloride in 0.1 M HNO3, which is thought by some to dissolve mostly the highly soluble Mn-oxides was found to also dissolve goethite, as did 0.25 M hydroxylamine hydrochloride in 25% (v/v) acetic acid, 0.25 M hydroxylamine hydrochloride in 0.25 M HCl, 0.5 M HCl, and Na-dithionite buffered with Na-citrate and 1.0 M NaHCO3. Both trace and major elements that were extracted with the various treatments were found to vary significantly and non-systematically when compared to the proportion of total extractable Fe. These selective extractions cannot be used to make reliable conclusions about trace metal and mineral associations. Gypsum was identified by XRD in clay-size separations from the sample, but this phase was not detected in diffraction scans of the bulk sample. This finding indicates that individual phases can be segregated by particle size. (C) 1998 Elsevier Science Ltd. All rights reserved.
BibTeX: @article{McCarty1998, author = {McCarty, DK and Moore, JN and Marcus, WA}, title = {Mineralogy and trace element association in an acid mine drainage iron oxide precipitate; comparison of selective extractions}, journal = {Applied Geochemistry}, year = {1998}, volume = {13}, number = {2}, pages = {165--176} }
Mcdowell2001	McDowell, P. Dorava, J. & others (Hrsg.)	Spatial variation of channel morphology at the segment and reach scales, Middle Fork of the John Day River, northeastern Oregon ( Geomorphic Processes and Riverine Habitat ) [BibTeX] [PDF]	2001	Geomorphic Processes and Riverine Habitat Vol. 4 , pp. 159-172	inbook	fluvial geomorphology
BibTeX: @inbook{Mcdowell2001, author = {McDowell, PF}, title = {Geomorphic Processes and Riverine Habitat}, publisher = {American Geophysical Union}, year = {2001}, volume = {4}, pages = {159-172} }
McDowell2000	McDowell, P. American Water Resources Association	Human impacts and river channel adjustment, northeastern Oregon: implications for restoration [BibTeX] [PDF]	2000	Riparian Ecology and Management in Multi-Land Use Watersheds Symposium Proceedings, Annual International Summer Specialty Conference, August 27-30, 2000	inproceedings	fluvial geomorphology
BibTeX: @inproceedings{McDowell2000, author = {McDowell, PF}, title = {Human impacts and river channel adjustment, northeastern Oregon: implications for restoration}, booktitle = {Riparian Ecology and Management in Multi-Land Use Watersheds Symposium Proceedings, Annual International Summer Specialty Conference, August 27-30, 2000}, year = {2000} }
McDowell1983	McDowell, P.	Evidence of stream response to Holocene climatic change in a small Wisconsin watershed [BibTeX]	1983	Quaternary Research Vol. 19 (1) , pp. 100-116	article
BibTeX: @article{McDowell1983, author = {McDowell, PF}, title = {Evidence of stream response to Holocene climatic change in a small Wisconsin watershed}, journal = {Quaternary Research}, year = {1983}, volume = {19}, number = {1}, pages = {100--116} }
McDowell2001	McDowell, P. & Edwards, M.	Evidence of Quaternary climatic variations in a sequence of loess and related deposits at Birch Creek, Alaska: implications for the Stage 5 climatic chronology [Abstract] [BibTeX] [PDF]	2001	Quaternary Science Reviews Vol. 20 (1-3) , pp. 63-76	article	paleoecology and paleoclimatology
Abstract: A 45 m outcrop of Quaternary sediments on Birch Creek, near Circle, Alaska, reveals a record of fluctuating environmental conditions that probably spans several glacial-interglacial cycles. From base to top the deposits are forested floodplain (warm), colluvium with ice wedges (cold), forest soil (warm)? loess (cold), paleosol containing Old Crow Tephra (OCt) (cool-to-warm), loess (cold), lacustrine (very warm), loess (cold), and modern forest soil (warm). Resolution of the paleoclimatic history associated with the OCt event is critical to understanding the nature of stage 5 in the western North American Arctic. Application of recent age estimates for the OCt tephra (ca. 140,000 yr BP) to the Birch Creek section would indicate that either (i) the tephra/paleosol dates from the 6/5.5 transition, a strongly developed glacial interval occurred within stage 5, and the overlying very warm interval occurred in 5.3 or 5.1, or (ii) the tephra was deposited during a "non-Milankovitch" warming event late in stage 6. A paleoclimate chronology provides an alternative interpretation, (iii), in which the tephra/paleosol corresponds to stage 6 or even stage 7, the overlying loess to stage 6, and the lake sediments to all or part of stage 5, but the OCt is older than 140,000 yr BP. Chronologies (ii) and (iii) imply a very warm beginning to stage 5, consistent with paleoclimate model simulations and data from other regions. (C) 2000 Elsevier Science Ltd. All rights reserved.
BibTeX: @article{McDowell2001, author = {McDowell, PF and Edwards, ME}, title = {Evidence of Quaternary climatic variations in a sequence of loess and related deposits at Birch Creek, Alaska: implications for the Stage 5 climatic chronology}, journal = {Quaternary Science Reviews}, year = {2001}, volume = {20}, number = {1-3}, pages = {63--76} }
Mcdowell1997	McDowell, P. & Magilligan, F.	Response of Stream Channels to Removal of Cattle Grazing Disturbance: Overview of Western U.S. Exclosure Studies ( Management of Landscapes Disturbed by Channel Incision ) [BibTeX] [PDF]	1997	Management of Landscapes Disturbed by Channel Incision , pp. 469-475	inbook	fluvial geomorphology
BibTeX: @inbook{Mcdowell1997, author = {McDowell, PF and Magilligan, FJ}, title = {Management of Landscapes Disturbed by Channel Incision}, year = {1997}, pages = {469-475} }
Millspaugh2004	Millspaugh, S.; C, W. & PJ, B. Wallace, L. (Hrsg.)	Postglacial fire, vegetation, and climate history of the Yellowstone-Lamar and Central Plateau Provinces, Yellowstone National Park ( After the Fires, The Ecology of Change in Yellowstone National Park ) [BibTeX]	2004	After the Fires, The Ecology of Change in Yellowstone National Park Vol. l , pp. 10-28	inbook	fire: modern and paleo
BibTeX: @inbook{Millspaugh2004, author = {Millspaugh, SH and Whitlock C and Bartlein PJ}, title = {After the Fires, The Ecology of Change in Yellowstone National Park}, publisher = {Yale University Press, New Haven}, year = {2004}, volume = {l}, pages = {10-28} }
Millspaugh2000	Millspaugh, S.; Whitlock, C. & Bartlein, P.	Variations in fire frequency and climate over the past 17 000 yr in central Yellowstone National Park [Abstract] [BibTeX] [Figures] [PDF]	2000	Geology Vol. 28 (3) , pp. 211-214	article
Abstract: A 17000 yr fire history from Yellowstone National Park demonstrates a strong link between changes in climate and variations in fire frequency on millennial time scales. The the history reconstruction is based on a detailed charcoal stratigraphy from Cygnet Lake in the rhyolite plateau region. Macroscopic charcoal particles were tallied from contiguous 1 cm samples of a 6.69-m-long core, and the data were converted to charcoal-accumulation rates at evenly spaced time intervals. Intervals of high charcoal-accumulation rates were interpreted as local fire events on the basis of information obtained from modern charcoal-calibration studies in the Yellowstone region. The record indicates that fire frequency was moderate (4 fires/1000 yr) during the late glacial period, reached highest values in the early Holocene (>10 tires/1000 yr), and decreased after 7000 calendar Sr B.P. The present fire regime (2-3 fires/1000 yr) was established in the past 2000 Sr The charcoal stratigraphy correlates well with variations in July insolation through time, which suggests that regional climate changes are responsible for the long-term variations in fire frequency. In the early Holocene, summer insolation was near its maximum, which resulted in warmer, effectively drier conditions throughout the northwestern United States. At this time, the fire frequency near Cygnet Lake was at its highest. After 7000 calendar ST B.P., summer insolation decreased to present values, the regional climate became cooler and wetter, and fires were less frequent. The Cygnet Lake record suggests that long-term fire frequencies have varied continuously with climate change, even when the vegetation has remained constant.
BibTeX: @article{Millspaugh2000, author = {Millspaugh, SH and Whitlock, C and Bartlein, PJ}, title = {Variations in fire frequency and climate over the past 17 000 yr in central Yellowstone National Park}, journal = {Geology}, year = {2000}, volume = {28}, number = {3}, pages = {211--214}, note = {http://geography.uoregon.edu/envchange/figures/Millspaugh-etal-Geology-2000-figs/index.html} }
Minckley2008	Minckley, T.; Bartlein, P.; Whitlock, C.; Shuman, B.; Williams, J. & Davis, O.	Associations among modern pollen, vegetation, and climate in western North America [Abstract] [BibTeX] [PDF]	2008	Quaternary Science Reviews Vol. 27 (21-22) , pp. 1962-1991	article
Abstract: A compilation of 1884 modern pollen surface samples was analyzed to explore the relationships between spatial distributions of pollen percentage data vs. climate and vegetation in western North America. Modern pollen spectra capture many of the unique traits of regional vegetation patterns and reflect regional patterns of climate diversity. Large-scale vegetation differences were identifiable by their pollen signatures. At the coarsest scale, forested regions were dominated by arboreal pollen and Pinus pollen abundances were typically >30%. In contrast, non-forested regions were dominated by shrub and herbaceous pollen types with Pinus percentages typically <30%. At finer scales, indicator taxa were useful for identifying vegetation types. For example, Picea was a good first-order indicator of boreal spruce forest vegetation with relatively high median percentages (22%), whereas Quercus was a good first-order indicator of desert vegetation with low median percentages (1%). Pollen abundance also provided climatic information. High Betula percentages occurred over a relatively narrow climatic range corresponding with their high latitudinal distribution, high Artemisia percentages were registered in winter-cold and dry climates of the interior basins. Arboreal pollen types were abundant in cool and wet climates, while non-arboreal pollen types dominate in climates that are warm and dry. Using pollen assemblages to predict local climate conditions shows that climate conditions are well predicted given knowledge of pollen spectra and climate conditions of the nearest analogues. Low accuracy was evident with pollen-based climate predictions in desert regions and temperate rainforests because of either poor sample density (in the case of the former) or extremes in temperature and/or precipitation (in the case of both). In other regions, vegetation and climate space were accurately predicted even when proximal samples, within 100 km, are excluded as the possible analogues. These results show that, within the vegetation and climate space of this region, the modern-analogue technique is useful for quantifying broad-scale vegetation and climate changes. (C) 2008 Elsevier Ltd. All rights reserved.
BibTeX: @article{Minckley2008, author = {Minckley, TA and Bartlein, PJ and Whitlock, C and Shuman, BN and Williams, JW and Davis, OK}, title = {Associations among modern pollen, vegetation, and climate in western North America}, journal = {Quaternary Science Reviews}, year = {2008}, volume = {27}, number = {21-22}, pages = {1962--1991} }
Minckley2007	Minckley, T.; Whitlock, C. & Bartlein, P.	Vegetation, fire, and climate history of the northwestern Great Basin during the last 14,000 years [Abstract] [BibTeX] [PDF]	2007	Quaternary Science Reviews Vol. 26 (17-18) , pp. 2167-2184	article
Abstract: The northwestern Great Basin lies in the transition zone between the mesic Pacific Northwest and xeric intermountain West. The paleoenvironruental history based on pollen, macroscopic charcoal, and plant macrofossils from three sites in the northwestern Great Basin was examined to understand the relationships among the modern vegetation, fire disturbance and climate. The vegetation history suggests that steppe and open forest communities were present at high elevations from ca 11,000 to 7000 cal yr BP, and were replaced by forests composed of white fir, western white pine, and whitebark pine in the late Holocene. Over the last 11,000 years, fires were more frequent in tuid-elevation forests (10-25 fire episodes/1000 years) and rare in high-elevation forests (2-5 fire episodes/1000 years). Applying modern pollen-climate relationships to the fossil pollen spectra provided a means to interpret past climate changes in this region. In the past 9000 years summer temperatures decreased from 1 to 4 C, and annual precipitation has increased 7-15%. These results indicate that the millennial-scale climate forcing driving vegetation changes can be quantified within the intermountain West in general and northwestern Great Basin in particular. In addition, fire call be considered an important component of these ecosystems, but it does not appear to be a forcing mechanism for vegetation change at the resolution of these records. (c) 2007 Elsevier Ltd. All rights reserved.
BibTeX: @article{Minckley2007, author = {Minckley, TA and Whitlock, C and Bartlein, PJ}, title = {Vegetation, fire, and climate history of the northwestern Great Basin during the last 14,000 years}, journal = {Quaternary Science Reviews}, year = {2007}, volume = {26}, number = {17-18}, pages = {2167--2184} }
Mock2000	Mock, C.	Rainfall in the Garden of the United States Great Plains; 1870-1889 [BibTeX] [PDF]	2000	Climatic Change Vol. 44 , pp. 173-195	article	human dimensions of climate change
BibTeX: @article{Mock2000, author = {Mock, CJ}, title = {Rainfall in the Garden of the United States Great Plains; 1870-1889}, journal = {Climatic Change}, year = {2000}, volume = {44}, pages = {173-195} }
Mock1996	Mock, C.	Climatic Controls and Spatial Variations of Precipitation in the Western United States [BibTeX] [Figures] [PDF]	1996	Journal of Climate Vol. 9 , pp. 1111-1125	article	synoptic climatology
BibTeX: @article{Mock1996, author = {Mock, CJ}, title = {Climatic Controls and Spatial Variations of Precipitation in the Western United States}, journal = {Journal of Climate}, year = {1996}, volume = {9}, pages = {1111-1125}, note = {http://geography.uoregon.edu/envchange/figures/Mock-JClimate-1996-figs/Jclimate.htm} }
Mock1995	Mock, C. & Bartlein, P.	Spatial variability of late-Quaternary paleoclimates in the western United States [Abstract] [BibTeX] [PDF]	1995	Quaternary Research Vol. 44 (3) , pp. 425-433	article	modern climate analogues
Abstract: Paleoclimatic interpretation of proxy data is complicated sometimes by the appearance of heterogeneous patterns of climatic responses across networks of sites. Modern climate analogues for the western United States, similar to those patterns of atmospheric circulation of 18,000 and 9000 yr B.P., were examined in order to explain such patterns of spatial heterogeneity, Modern analogues were defined by comparing modern atmospheric circulation patterns with those simulated by general circulation models, Maps of temperature and precipitation anomalies of the modern analogues reveal patterns of spatial heterogeneity, which resemble the patterns of effective moisture compiled from paleoclimatic data, January 1957 was found to be a reasonable 18,000 yr B.P. analogue, and it features isolated areas of increased wetness in the northern Great Basin and increased dryness in the Northwest interior, Analogues for 9000 yr B.P. from a composite of 11 Augusts display patterns of spatial heterogeneity of effective moisture over most of the mountainous areas, The analogues suggest that spatial heterogeneity of climate is the rule rather than the exception over much of the western United States, with the climatic anomalies at any particular time representing the outcome of the mediation of large-scale atmospheric circulation controls by smaller scale topographic features. (C) 1995 University of Washington.
BibTeX: @article{Mock1995, author = {Mock, CJ and Bartlein, PJ}, title = {Spatial variability of late-Quaternary paleoclimates in the western United States}, journal = {Quaternary Research}, year = {1995}, volume = {44}, number = {3}, pages = {425--433} }
Mock1998	Mock, C.; Bartlein, P. & Anderson, P.	Atmospheric circulation patterns and spatial climatic variations in Beringia [Abstract] [BibTeX] [Figures] [PDF]	1998	International Journal of Climatology Vol. 18 (10) , pp. 1085-1104	article	synoptic climatology
Abstract: Analyses of more than 40 years of climatic data reveal intriguing spatial variations in climatic patterns for Beringia (North-eastern Siberia and Alaska), aiding the understanding of the hierarchy of climatic controls that operate at different spatial scales within the Arctic. A synoptic climatology, using a subjective classification methodology on January and July sea level pressure, and July 500 hPa height anomaly patterns, identified 13 major atmospheric circulation patterns (26 pairs consisting of 13 synoptic/temperature and 13 synoptic/precipitation comparisons) that occur over Beringia. Composite anomaly maps of circulation, temperature, and precipitation described the spatial variability of surface climatic responses to circulation. Results indicate that nine synoptic pairs yield homogeneous surface climatic anomaly patterns throughout most of Beringia. However, many of the surface climatic responses illustrate heterogeneous anomaly patterns as a result of variations in circulation controls, such as troughing over East Asia and the Pacific subtropical high superimposed over topography, with small shifts in atmospheric circulation dramatically altering spatial variations of anomaly patterns. Distinctive contrasts in climatic responses, as suggested from ten synoptic pairs, are clearly evident for Western Beringia versus Eastern Beringia. These results offer important implications for scholars interested in assessing late Quaternary climatic change in the region from interannual to millennial timescales. (C) 1998 Royal Meteorological Society.
BibTeX: @article{Mock1998, author = {Mock, CJ and Bartlein, PJ and Anderson, PM}, title = {Atmospheric circulation patterns and spatial climatic variations in Beringia}, journal = {International Journal of Climatology}, year = {1998}, volume = {18}, number = {10}, pages = {1085--1104}, note = {http://geography.uoregon.edu/envchange/figures/Mock-etal-IntJClim-1998-figs/IntJClim.htm} }
Mooney2011	Mooney, S.; Harrison, S.; Bartlein, P.; Daniau, A.; Stevenson, J.; Brownlie, K.; Buckman, S.; Cupper, M.; Luly, J.; Black, M.; Colhoun, E.; D'Costa, D.; Dodson, J.; Haberle, S.; Hope, G.; Kershaw, P.; Kenyon, C.; McKenzie, M. & Williams, N.	Late Quaternary fire regimes of Australasia [Abstract] [BibTeX]	2011	Quaternary Science Reviews Vol. 30 (1-2) , pp. 28-46	article	fire: paleo and modern
Abstract: We have compiled 223 sedimentary charcoal records from Australasia in order to examine the temporal and spatial variability of fire regimes during the Late Quaternary. While some of these records cover more than a full glacial cycle, here we focus on the last 70,000 years when the number of individual records in the compilation allows more robust conclusions. On orbital time scales, fire in Australasia predominantly reflects climate, with colder periods characterized by less and warmer intervals by more biomass burning. The composite record for the region also shows considerable millennial-scale variability during the last glacial interval (73.5-14.7 ka). Within the limits of the dating uncertainties of individual records, the variability shown by the composite charcoal record is more similar to the form, number and timing of Dansgaard-Oeschger cycles as observed in Greenland ice cores than to the variability expressed in the Antarctic ice-core record. The composite charcoal record suggests increased biomass burning in the Australasian region during Greenland Interstadials and reduced burning during Greenland Stadials. Millennial-scale variability is characteristic of the composite record of the subtropical high pressure belt during the past 21 ka, but the tropics show a somewhat simpler pattern of variability with major peaks in biomass burning around 15 ka and 8 ka. There is no distinct change in fire regime corresponding to the arrival of humans in Australia at 50 +/- 10 ka and no correlation between archaeological evidence of increased human activity during the past 40 ka and the history of biomass burning. However, changes in biomass burning in the last 200 years may have been exacerbated or influenced by humans. (C) 2010 Elsevier Ltd. All rights reserved.
BibTeX: @article{Mooney2011, author = {Mooney, SD and Harrison, SP and Bartlein, PJ and Daniau, AL and Stevenson, J and Brownlie, KC and Buckman, S and Cupper, M and Luly, J and Black, M and Colhoun, E and D'Costa, D and Dodson, J and Haberle, S and Hope, GS and Kershaw, P and Kenyon, C and McKenzie, M and Williams, N}, title = {Late Quaternary fire regimes of Australasia}, journal = {Quaternary Science Reviews}, year = {2011}, volume = {30}, number = {1-2}, pages = {28--46} }
Oswald2003	Oswald, W.; Brubaker, L.; Hu, F. & Gavin, D.	Pollen-vegetation calibration for tundra communities in the Arctic Foothills, northern Alaska [Abstract] [BibTeX] [PDF]	2003	Journal of Ecology Vol. 91 (6) , pp. 1022-1033	article
Abstract: 1 Palynology has been portrayed as a 'blunt' tool for reconstructing variations in arctic tundra vegetation. We tested this characterization in the Arctic Foothills of northern Alaska by analysing 56 modern pollen assemblages from lakes on contrasting glaciated surfaces. The two surfaces, which date to the Sagavanirktok (> 125 000 years BP) and Itkillik II (c. 11 500 years BP) ice advances from the Brooks Range, have considerably different geomorphology, soil characteristics and plant communities. Sagavanirktok surfaces are dominated by dwarf-shrub tundra (DST), and Itkillik II surfaces by prostrate-shrub tundra (PST). 2 We used two multivariate approaches, dissimilarity metrics (squared chord distance and Canberra metric distance) and discriminant analysis, to assess the ability of the pollen data to distinguish between the Sagavanirktok and Itkillik II landscapes, and to identify the taxa most strongly associated with one surface or the other. Receiver operating characteristic (ROC) analysis was used to evaluate the performance of the dissimilarity metrics and to determine their 'critical values' for distinguishing between assemblages from like and unlike plant communities. 3 According to the discriminant analysis, taxa indicative of the Sagavanirktok surface include Rubus chamaemorus, Sphagnum and Ericales, whereas Equisetum, Thalictrum and Polypodiaceae were faithful to the Itkillik II surface. These differences between the pollen assemblages make it possible to differentiate between the two landscapes using Canberra metric distance comparisons. The ROC analysis demonstrated that the Canberra metric distance is more effective than squared chord distance for distinguishing between the two surfaces. This study illustrates that palynology can be used to explore questions regarding the landscape-scale heterogeneity of past tundra vegetation.
BibTeX: @article{Oswald2003, author = {Oswald, WW and Brubaker, LB and Hu, FS and Gavin, DG}, title = {Pollen-vegetation calibration for tundra communities in the Arctic Foothills, northern Alaska}, journal = {Journal of Ecology}, year = {2003}, volume = {91}, number = {6}, pages = {1022--1033} }
Overpeck1991	Overpeck, J.; Bartlein, P. & Webb, T.	Potential magnitude of future vegetation change in eastern North America - comparisons with the past [Abstract] [BibTeX]	1991	Science Vol. 254 (5032) , pp. 692-695	article
Abstract: Increases in atmospheric trace gas concentrations could warm the global average temperature 1.5-degrees to 4.5-degrees-C by the end of the next century. Application of climate-pollen response surfaces to three climate model simulations of doubled preindustrial atmospheric CO2 levels shows that the change in the equilibrium distribution of natural vegetation over eastern North America over the next 200 to 500 years could be larger than the overall change during the past 7,000 to 10,000 years and equivalent to the change that took place over the 1,000- to 3,000-year period of most rapid deglaciation. Some plant ranges and abundance maxima could shift as much as 500 to 1000 km during the next 200 to 500 years; such changes would have dramatic impacts on silvicultural and natural ecosystems. Although unprecedented vegetation change is likely if climate changes as predicted, forecasting the exact timing and patterns of change will be difficult.
BibTeX: @article{Overpeck1991, author = {Overpeck, JT and Bartlein, PJ and Webb, T}, title = {Potential magnitude of future vegetation change in eastern North America - comparisons with the past}, journal = {Science}, year = {1991}, volume = {254}, number = {5032}, pages = {692--695} }
Power2010	Power, M.; Marlon, J.; Bartlein, P. & Harrison, S.	Fire history and the Global Charcoal Database: A new tool for hypothesis testing and data exploration [Abstract] [BibTeX]	2010	Palaeogeography Palaeoclimatology Palaeoecology Vol. 291 (1-2) , pp. 52-59	article
Abstract: Version 1 of the Global Charcoal Database is now available for regional fire history reconstructions, data exploration, hypothesis testing, and evaluation of coupled climate-vegetation-fire model simulations. The charcoal database contains over 400 radiocarbon-dated records that document changes in charcoal abundance during the Late Quaternary. The aim of this public database is to stimulate cross-disciplinary research in fire sciences targeted at an increased understanding of the controls and impacts of natural and anthropogenic fire regimes on centennial-to-orbital timescales. We describe here the data standardization techniques for comparing multiple types of sedimentary charcoal records. Version 1 of the Global Charcoal Database has been used to characterize global and regional patterns in fire activity since the last glacial maximum. Recent studies using the charcoal database have explored the relation between climate and fire during periods of rapid climate change, including evidence of fire activity during the Younger Dryas Chronozone, and during the past two millennia. Published by Elsevier B.V.
BibTeX: @article{Power2010, author = {Power, MJ and Marlon, JR and Bartlein, PJ and Harrison, SP}, title = {Fire history and the Global Charcoal Database: A new tool for hypothesis testing and data exploration}, journal = {Palaeogeography Palaeoclimatology Palaeoecology}, year = {2010}, volume = {291}, number = {1-2}, pages = {52--59} }
Power2008	Power, M.; Marlon, J.; Ortiz, N.; Bartlein, P.; Harrison, S.; Mayle, F.; Ballouche, A.; Bradshaw, R.; Carcaillet, C.; Cordova, C.; Mooney, S.; Moreno, P.; Prentice, I.; Thonicke, K.; Tinner, W.; Whitlock, C.; Zhang, Y.; Zhao, Y.; Ali, A.; Anderson, R.; Beer, R.; Behling, H.; Briles, C.; Brown, K.; Brunelle, A.; Bush, M.; Camill, P.; Chu, G.; Clark, J.; Colombaroli, D.; Connor, S.; Daniau, A.; Daniels, M.; Dodson, J.; Doughty, E.; Edwards, M.; Finsinger, W.; Foster, D.; Frechette, J.; Gaillard, M.; Gavin, D.; Gobet, E.; Haberle, S.; Hallett, D.; Higuera, P.; Hope, G.; Horn, S.; Inoue, J.; Kaltenrieder, P.; Kennedy, L.; Kong, Z.; Larsen, C.; Long, C.; Lynch, J.; Lynch, E.; McGlone, M.; Meeks, S.; Mensing, S.; Meyer, G.; Minckley, T.; Mohr, J.; Nelson, D.; New, J.; Newnham, R.; Noti, R.; Oswald, W.; Pierce, J.; Richard, P.; Rowe, C.; Goni, M.; Shuman, B.; Takahara, H.; Toney, J.; Turney, C.; Urrego-Sanchez, D.; Umbanhowar, C.; Vandergoes, M.; Vanniere, B.; Vescovi, E.; Walsh, M.; Wang, X.; Williams, N.; Wilmshurst, J. & Zhang, J.	Changes in fire regimes since the Last Glacial Maximum: an assessment based on a global synthesis and analysis of charcoal data [Abstract] [BibTeX] [PDF]	2008	Climate Dynamics Vol. 30 (7-8) , pp. 887-907	article
Abstract: Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial period, from 21,000 to similar to 11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present fire activity from similar to 19,000 to similar to 17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to similar to 13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8,000 to similar to 3,000 cal yr BP, Indonesia and Australia from 11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.
BibTeX: @article{Power2008, author = {Power, MJ and Marlon, J and Ortiz, N and Bartlein, PJ and Harrison, SP and Mayle, FE and Ballouche, A and Bradshaw, RHW and Carcaillet, C and Cordova, C and Mooney, S and Moreno, PI and Prentice, IC and Thonicke, K and Tinner, W and Whitlock, C and Zhang, Y and Zhao, Y and Ali, AA and Anderson, RS and Beer, R and Behling, H and Briles, C and Brown, KJ and Brunelle, A and Bush, M and Camill, P and Chu, GQ and Clark, J and Colombaroli, D and Connor, S and Daniau, AL and Daniels, M and Dodson, J and Doughty, E and Edwards, ME and Finsinger, W and Foster, D and Frechette, J and Gaillard, MJ and Gavin, DG and Gobet, E and Haberle, S and Hallett, DJ and Higuera, P and Hope, G and Horn, S and Inoue, J and Kaltenrieder, P and Kennedy, L and Kong, ZC and Larsen, C and Long, CJ and Lynch, J and Lynch, EA and McGlone, M and Meeks, S and Mensing, S and Meyer, G and Minckley, T and Mohr, J and Nelson, DM and New, J and Newnham, R and Noti, R and Oswald, W and Pierce, J and Richard, PJH and Rowe, C and Goni, MFS and Shuman, BN and Takahara, H and Toney, J and Turney, C and Urrego-Sanchez, DH and Umbanhowar, C and Vandergoes, M and Vanniere, B and Vescovi, E and Walsh, M and Wang, X and Williams, N and Wilmshurst, J and Zhang, JH}, title = {Changes in fire regimes since the Last Glacial Maximum: an assessment based on a global synthesis and analysis of charcoal data}, journal = {Climate Dynamics}, year = {2008}, volume = {30}, number = {7-8}, pages = {887--907} }
Power2006	Power, M.; Whitlock, C.; Bartlein, P. & Stevens, L.	Fire and vegetation history during the last 3800 years in northwestern Montana [Abstract] [BibTeX]	2006	Geomorphology Vol. 75 (3-4) , pp. 420-436	article
Abstract: Foy Lake in northwestern Montana provides a record of annual-to-decadal-scale landscape change. Sedimentary charcoal and pollen analyses were used to document fire and vegetation changes over the last 3800 years, which were then compared to similar records from AD 1880 to 2000. The long-term record at Foy Lake suggests shifts between forest and steppe as well as changes in fire regime that are likely the result of climate change. Fire activity (inferred from the frequency of charcoal peaks) averaged 18 fire episodes/1000 years from 3800 to 2125 cal year BP, and increased from 16 fire episodes/1000 years at 2125 cal year BP to 22 episodes/1000 years at 750 cal year BP, a period when the pollen data suggest that steppe vegetation yielded to increasing patches of forest cover. Between 2125 and 750 cal year BP, increased forest cover produced more background charcoal than before and after this period, when vegetation was dominated by steppe. Between 750 and 75 cal year BP steppe has expanded and fire episode frequency averaged 33 episodes/1000 years, increasing to a maximum of 40 episodes/1000 years at ca. 300 cal year BP and then decreasing to present levels. Since AD 1880, the pollen record indicates an increase in shrubs and grasses from AD 1895 to 1960 as a result of vegetation changes associated with timber harvesting and livestock grazing. No fires have been documented in the Foy Lake watershed since AD 1880. Charcoal from the extralocal fires of AD 1910, burning over 4,111,249 ha in Idaho, Montana, and Wyoming, however, is present in Foy Lake. Between AD 1970 and 2000, increased arboreal pollen in the record is consistent with observations that the forest has become more closed. The activities of Euro-Americans have led to a decline in forest cover between AD 1880 and 1970, followed by a recent increase as trees are now growing in areas previously occupied by steppe. Euro-Americans are likely the cause of a reduction in fire activity in watershed since AD 1880. (c) 2005 Elsevier B.V. All rights reserved.
BibTeX: @article{Power2006, author = {Power, MJ and Whitlock, C and Bartlein, P and Stevens, LR}, title = {Fire and vegetation history during the last 3800 years in northwestern Montana}, journal = {Geomorphology}, year = {2006}, volume = {75}, number = {3-4}, pages = {420--436} }
Prentice1991	Prentice, I.; Bartlein, P. & Webb, T.	Vegetation and climate change in eastern North America since the last glacial maximum [Abstract] [BibTeX] [PDF]	1991	Ecology Vol. 72 (6) , pp. 2038-2056	article
Abstract: Response surfaces describing the empirical dependence of surface pollen percentages of 13 taxa on three standard climatic variables (mean July temperature, mean January temperature, and mean annual precipitation) in eastern North America were used to infer past climates from palynological data. Inferred climates at 3000-yr intervals from 18 000 years ago to the present, based on six taxa (spruce, birch, northern pines, oak, southern pines, and prairie forbs), were used to generate time series of simulated isopoll maps for these taxa and seven others (hickory, fir, beech, hemlock, elm, alder, and sedge). The simulations captured the essential features of the observed isopoll maps for both sets of taxa, including differences in migration patterns during the past 10000 yr that have previously been attributed to differential migration lag. These results establish that the continental-scale vegetation patterns have responded to continuous changes in climate from the last glacial maximum to the present, with lags less-than-or-equal-to 1500 yr. The inferred climatic changes include seasonality changes consistent with orbitally controlled changes in insolation, and shifts in temperature and moisture gradients that are consistent with modelled climatic interactions of the insolation changes with the shrinking Laurentide ice sheet. These results pose new ecological questions about the processes by which vegetated landscapes approach dynamic equilibrium with their changing environment.
BibTeX: @article{Prentice1991, author = {Prentice, IC and Bartlein, PJ and Webb, T}, title = {Vegetation and climate change in eastern North America since the last glacial maximum}, journal = {Ecology}, year = {1991}, volume = {72}, number = {6}, pages = {2038--2056} }
Prentice2011	Prentice, I.; Harrison, S. & Bartlein, P.	Global vegetation and terrestrial carbon cycle changes after the last ice age [Abstract] [BibTeX]	2011	New Phytologist Vol. 189 (4) , pp. 988-998	article
Abstract: In current models, the ecophysiological effects of CO2 create both woody thickening and terrestrial carbon uptake, as observed now, and forest cover and terrestrial carbon storage increases that took place after the last glacial maximum (LGM). Here, we aimed to assess the realism of modelled vegetation and carbon storage changes between LGM and the pre-industrial Holocene (PIH). We applied Land Processes and eXchanges (LPX), a dynamic global vegetation model (DGVM), with lowered CO2 and LGM climate anomalies from the Palaeoclimate Modelling Intercomparison Project (PMIP II), and compared the model results with palaeodata. Modelled global gross primary production was reduced by 27-36% and carbon storage by 550-694 Pg C compared with PIH. Comparable reductions have been estimated from stable isotopes. The modelled areal reduction of forests is broadly consistent with pollen records. Despite reduced productivity and biomass, tropical forests accounted for a greater proportion of modelled land carbon storage at LGM (28-32%) than at PIH (25%). The agreement between palaeodata and model results for LGM is consistent with the hypothesis that the ecophysiological effects of CO2 influence tree-grass competition and vegetation productivity, and suggests that these effects are also at work today.
BibTeX: @article{Prentice2011, author = {Prentice, IC and Harrison, SP and Bartlein, PJ}, title = {Global vegetation and terrestrial carbon cycle changes after the last ice age}, journal = {New Phytologist}, year = {2011}, volume = {189}, number = {4}, pages = {988--998} }
Prentice1993	Prentice, I.; Sykes, M.; Lautenschlager, M.; Harrison, S.; Denisekko, O. & BARTLEIN, P.	Modeling global vegetation patterns and terrestrial carbon storage at the Last Glacial Maximum [Abstract] [BibTeX]	1993	Global Ecology and Biogeography Letters Vol. 3 (3) , pp. 67-76	article
Abstract: Global patterns of potential natural vegetation were simulated for present and last glacial maximum (LGM) climates. The LGM simulation showed good agreement with available evidence, most importantly in the humid tropics. Simple calculations based on these simulations indicate that terrestrial carbon storage increased by 300-700 Pg C after the LGM. The range is due to uncertainties in the mean carbon storage values for different biomes, and in the amount of carbon in boreal peats. These results are consistent with the global change in ocean delta-C-13, inferred from measurements on benthic foraminifera, reflecting the increased storage of isotopically light carbon on land.
BibTeX: @article{Prentice1993, author = {Prentice, IC and Sykes, MT and Lautenschlager, M and Harrison, SP and Denisekko, O and BARTLEIN, PJ}, title = {Modeling global vegetation patterns and terrestrial carbon storage at the Last Glacial Maximum}, journal = {Global Ecology and Biogeography Letters}, year = {1993}, volume = {3}, number = {3}, pages = {67--76} }
Retallack1988	Retallack, G. & McDowell, P.	Penrose conference report - paleoenvironmental interpretation of paleosols [BibTeX]	1988	Geology Vol. 16 (4) , pp. 375-376	article
BibTeX: @article{Retallack1988, author = {Retallack, G and McDowell, P}, title = {Penrose conference report - paleoenvironmental interpretation of paleosols}, journal = {Geology}, year = {1988}, volume = {16}, number = {4}, pages = {375--376} }
Shafer2001	Shafer, S.; Bartlein, P. & Thompson, R.	Potential changes in the distributions of western North America tree and shrub taxa under future climate scenarios [Abstract] [BibTeX] [PDF]	2001	Ecosystems Vol. 4 (3) , pp. 200-215	article	future vegetation changes
Abstract: Increases in atmospheric greenhouse gases are driving significant changes in global climate. To project potential vegetation response to future climate change, this study uses response surfaces to describe the relationship between bioclimatic variables and the distribution of tree and shrub taxa in western North America. The response surfaces illustrate the probability of the occurrence of a taxon at particular points in climate space. Climate space was defined using three bioclimatic variables: mean temperature of the coldest month, growing degree days, and a moisture index. Species distributions were simulated under present climate using observed data (1951-80, 30-year mean) and under future climate (2090-99, 10-year mean) using scenarios generated by three general circulation models-HADCM2, CGCM1, and CSIRO. The scenarios assume a 1% per year compound increase in greenhouse gases and changes in sulfate (SO4) aerosols based on the Intergovernmental Panel on Climate Change (IPCC) IS92a scenario. The results indicate that under future climate conditions, potential range changes could be large for many tree and shrub taxa. Shifts in the potential ranges of species are simulated to occur not only northward but in all directions, including southward of the existing ranges of certain species. The simulated potential distributions of some species become increasingly fragmented under the future climate scenarios, while the simulated potential distributions of other species expand. The magnitudes of the simulated range changes imply significant impacts to ecosystems and shifts in patterns of species diversity in western North America.
BibTeX: @article{Shafer2001, author = {Shafer, SL and Bartlein, PJ and Thompson, RS}, title = {Potential changes in the distributions of western North America tree and shrub taxa under future climate scenarios}, journal = {Ecosystems}, year = {2001}, volume = {4}, number = {3}, pages = {200--215} }
Shafer2005	Shafer, S.; Bartlein, P. & Whitlock, C. Huber, U.; Reasoner, M. & Bugmann, H. (Hrsg.)	Understanding the spatial heterogeneity of global environmental change in mountain regions ( Global Change and Mountain Regions ) [BibTeX] [PDF]	2005	Global Change and Mountain Regions	inbook	future vegetation changes
BibTeX: @inbook{Shafer2005, author = {Shafer, SL and Bartlein, PJ and Whitlock, C}, title = {Global Change and Mountain Regions}, publisher = {Springer, Heidelburg}, year = {2005} }
Shafer1998	Shafer, S. & Murphy, A.	The Territorial Strategies of IGO's: Implications for Environment and Development [BibTeX] [Figures]	1998	Global Governance Vol. 4 , pp. 257-274	article	human dimensions of climate change
BibTeX: @article{Shafer1998, author = {Shafer, SL and Murphy, AB}, title = {The Territorial Strategies of IGO's: Implications for Environment and Development}, journal = {Global Governance}, year = {1998}, volume = {4}, pages = {257-274}, note = {http://geography.uoregon.edu/envchange/figures/Shafer-and-Murphy-GlobalGov-1998-figs/igo.html} }
Shinker2010	Shinker, J. & Bartlein, P.	Spatial variations of effective moisture in the western United States [Abstract] [BibTeX]	2010	Geophysical Research Letters Vol. 37 , pp. -	article
Abstract: Spatial patterns of actual evapotranspiration (AE), potential evapotranspiration (PE), and their ratio (AE/PE) in the western United States are examined to describe the annual cycle of moisture availability. Long-term (1971-2000) averages of observed temperature and precipitation, and sunshine data were used to calculate AE and PE. A cluster analysis identifies regions with similar annual cycles of AE/PE. We identify three different spatial scales of variability in AE/PE: (1) broadscale patterns reflect the trade-off between winter-dominated precipitation of the Pacific Northwest and summer-dominated precipitation east of the Rocky Mountains, and the south-to-north decrease in PE related to latitudinal variations in net radiation; (2) mesoscale patterns show the influence of regional-scale features (e. g., the North American Monsoon); and (3) local-scale patterns are related to topography. Understanding the scales of effective-moisture variations is valuable from the perspective of terrestrial ecosystems and water resources management in the mostly arid western United States. Citation: Shinker, J.J., and P.J. Bartlein (2010), Spatial variations of effective moisture in the western United States, Geophys. Res. Lett., 37, L02701, doi:10.1029/2009GL041387.
BibTeX: @article{Shinker2010, author = {Shinker, JJ and Bartlein, PJ}, title = {Spatial variations of effective moisture in the western United States}, journal = {Geophysical Research Letters}, year = {2010}, volume = {37}, pages = {--} }
Shinker2009	Shinker, J. & Bartlein, P.	Visualizing the Large-Scale Patterns of ENSO-Related Climate Anomalies in North America [Abstract] [BibTeX]	2009	Earth Interactions Vol. 13 , pp. -	article
Abstract: The variations of large-scale climatic controls and surface responses through the annual cycle during strong positive (El Nino) and negative (La Nina) phase ENSO events are analyzed to assess the within-year and among-year variations of climate anomalies. Data from the NCEP-NCAR reanalysis project are presented as small-multiple maps to illustrate the spatial and temporal variability in North American climate associated with extreme phases of ENSO. Temperature, mean sea level pressure, 500-mb geopotential heights, and 850-mb specific humidity have composite-anomaly patterns that exhibit the greatest degree of spatial and temporal coherence. In general, the composite-anomaly patterns for El Nino and La Nina events are of opposite sign, with stronger, more spatially coherent anomalies occurring during El Nino events than during La Nina events. However, the strength and coherency of the precipitation anomaly patterns are reduced in the interior intermountain west during both positive and negative phase of ENSO. The variations in precipitation anomalies are compared to the 500-mb omega and 850-mb specific humidity composite-anomaly patterns, which provide information on the controls of precipitation by large-scale vertical motions and moisture availability thus providing information on the specific mechanisms associated with precipitation variability during ENSO events.
BibTeX: @article{Shinker2009, author = {Shinker, JJ and Bartlein, PJ}, title = {Visualizing the Large-Scale Patterns of ENSO-Related Climate Anomalies in North America}, journal = {Earth Interactions}, year = {2009}, volume = {13}, pages = {--} }
Shinker2006	Shinker, J.; Bartlein, P. & Shuman, B.	Synoptic and dynamic climate controls of North American mid-continental aridity [Abstract] [BibTeX]	2006	Quaternary Science Reviews Vol. 25 (13-14) , pp. 1401-1417	article
Abstract: The mid-continent of North America was likely drier than present during the mid-Holocene, based on inferences from fossil-pollen data and estimates of past lake levels. Mid-Holocene dry conditions have often been explained by increases in the dominance (frequency and/or duration) of Pacific airmasses, zonal flow patterns, or enhanced westerlies. We analyzed modern episodes between 1959 and 1997 when westerly flow was anomalously strong (an indication of zonal flow) to determine if zonal flow is associated with drier-than-normal conditions in the mid-continent. In contrast to that expectation, composite-anomaly patterns of 500mb geopotential heights show similar meridional, as opposed to zonal, patterns for both anomalously dry and anomalously wet years, suggesting that large-scale circulation patterns alone may not provide a full explanation of surface-moisture anomalies. Anomalous moisture conditions in the midcontinent at present develop due to the dynamic interplay between surface conditions and atmospheric processes. Consideration of both moisture availability (determined by atmospheric moisture flux and soil-moisture recycling) and mechanisms for enhancing or suppressing precipitation (vertical motions in the atmosphere) is therefore required to describe the establishment of anomalously dry or wet conditions in the region today, as well as during the mid-Holocene. (c) 2006 Elsevier Ltd. All rights reserved.
BibTeX: @article{Shinker2006, author = {Shinker, JJ and Bartlein, PJ and Shuman, B}, title = {Synoptic and dynamic climate controls of North American mid-continental aridity}, journal = {Quaternary Science Reviews}, year = {2006}, volume = {25}, number = {13-14}, pages = {1401--1417} }
Shuman2002	Shuman, B.; Bartlein, P.; Logar, N.; Newby, P. & Webb, T.	Parallel climate and vegetation responses to the early Holocene collapse of the Laurentide Ice Sheet [Abstract] [BibTeX] [Figures] [PDF]	2002	Quaternary Science Reviews Vol. 21 (16-17) , pp. 1793-1805	article	paleoclimatic analysis and data-model comparisons
Abstract: Parallel changes in lake-level and pollen data show that the rapid decline of the Laurentide Ice Sheet (LIS) between 10,000 and 8000 cal yr BP triggered a step-like change in North American climates: from an ice-sheet-and-insolation-dominated climate to a climate primarily controlled by insolation. Maps of the lake-level data from across eastern North America, show a reorganization of climate patterns that the pollen data independently match. Raised lake-levels and expanded populations of moist-tolerant southern pines (Pinus) document that summer monsoons intensified in the southeastern United States between 9000 and 8000 cal yr BP. Simultaneously, low lake-levels and an eastward expansion of the prairie illustrate an increase in mid-continental aridity. After the Hudson Bay ice dome collapsed around 8200 cal yr BP, lake-levels rose in New England, as populations of mesic plant taxa, such as beech (Fagus) and hemlock (Tsuga), replaced those of dry-tolerant northern pines (Pinus). Available moisture increased there after a related century-scale period of colder-than-previous conditions around 8200 cal yr BP, which is also recorded in the pollen data. The comparison between pollen and lake-level data confirms that vegetations dynamics reflect climatic patterns on the millennial-scale. (C) 2002 Elsevier Science Ltd. All rights reserved.
BibTeX: @article{Shuman2002, author = {Shuman, B and Bartlein, P and Logar, N and Newby, P and Webb, T}, title = {Parallel climate and vegetation responses to the early Holocene collapse of the Laurentide Ice Sheet}, journal = {Quaternary Science Reviews}, year = {2002}, volume = {21}, number = {16-17}, pages = {1793--1805}, note = {http://geography.uoregon.edu/envchange/figures/Shuman-etal-QSR-2002b-figs/} }
Shuman2007	Shuman, B.; Bartlein, P. & Webb, T.	Response to "Comments on: 'The magnitude of millennial-and orbital-scale climatic change in eastern North America during the Late-Quaternary' by Shuman et al." [BibTeX]	2007	Quaternary Science Reviews Vol. 26 (1-2) , pp. 268-273	article
BibTeX: @article{Shuman2007, author = {Shuman, B and Bartlein, PJ and Webb, T}, title = {Response to "Comments on: 'The magnitude of millennial-and orbital-scale climatic change in eastern North America during the Late-Quaternary' by Shuman et al."}, journal = {Quaternary Science Reviews}, year = {2007}, volume = {26}, number = {1-2}, pages = {268--273} }
Shuman2005	Shuman, B.; Bartlein, P. & Webb, T.	The magnitudes of millennial- and orbital-scale climatic change in eastern North America during the Late Quaternary [Abstract] [BibTeX] [PDF]	2005	Quaternary Science Reviews Vol. 24 (20-21) , pp. 2194-2206	article	paleoclimatic analysis and data-model comparisons
Abstract: Temporal differences among fossil pollen samples from eastern North America provide a measure of the amount of climatic change that occurred on a broad spatial scale since the last glacial maximum (21,000 cal yr BP). Square-chord distances (SCDs) quantify the difference between pollen samples, and, thus, represent the potential magnitude of climatic change underlying the pollen record. The magnitude varied significantly among time scales with small changes common at centennial to millennial scales and large changes common at multi-millennial (i.e. orbital) scales. SCDs measured across 3000-yr intervals averaged 0.20, and often exceeded the maximum difference expected from samples collected within the same biome (0.15). SCDs across individual millennia were smaller and averaged 0.08. SCDs across the millennia at the beginning (13,000-12,000cal yr BP) and end (12,000-11,000 cat yr BP) of the Younger Dryas chronozone (12,900-11,600 cal yr BP), however, averaged 0.20 and 0.18, respectively. These rapid step changes, large at sub-millennial scales, equal about 5-25% of the total glacial-interglacial transition. Large magnitude progressive changes in insolation, ice sheet extent, and atmospheric composition parallel the dominant trends in the SCD data, which show that progressive change comprises the first-order climatic pattern of the Holocene rather than stable or oscillatory patterns. (c) 2005 Elsevier Ltd. All rights reserved.
BibTeX: @article{Shuman2005, author = {Shuman, B and Bartlein, PJ and Webb, T}, title = {The magnitudes of millennial- and orbital-scale climatic change in eastern North America during the Late Quaternary}, journal = {Quaternary Science Reviews}, year = {2005}, volume = {24}, number = {20-21}, pages = {2194--2206} }
Shuman2002a	Shuman, B.; Thompson, W.; Bartlein, P. & Williams, J.	The anatomy of a climatic oscillation: vegetation change in eastern North America during the Younger Dryas chronozone [Abstract] [BibTeX] [Figures] [PDF]	2002	Quaternary Science Reviews Vol. 21 (16-17) , pp. 1777-1791	article	paleoclimatic analysis and data-model comparisons
Abstract: Century-scale climate changes reshaped circulation patterns over the North Atlantic and adjacent regions during the last glacial-to-interglacial transition. Here, we show that vegetation across eastern North America shifted dramatically at the beginning and end of the Younger Dryas chronozone (YDC: 12,900-11,600 cal yr B.P.), when changes in ocean circulation rapidly cooled and then warmed the North Atlantic sea-surface. On both the site-specific scale and the continental-scale, vegetation changed only gradually during the millennia before (15,000-13,000 cal yr B.P.) and after (11,000-9000 cal yr B.P.) the YDC, but climate changes ca 12,900 and 11,600 cal yr B.P. altered the vegetation on both spatial scales within centuries. Plant associations changed and some taxa rapidly migrated hundreds of kilometers (>300km within similar to100yr). In limited regions near the North Atlantic coast, abrupt cooling ca 12,900 cal yr B.P. resulted in a return to earlier vegetation types. Elsewhere, however, the vegetation patterns during the YDC were distinct from those of both earlier and later intervals. They indicate abrupt, 'non-reversing' seasonal temperature changes that were probably related to atmospheric circulation changes during the YDC, rather than to the direct influence of North Atlantic sea-surface temperatures. Atmospheric circulation patterns during the YDC were unique within the last 21,000yr because of a unique combination of climate controls. Insolation, ice sheet extent, and atmospheric composition were significantly different from their full-glacial states, even when the North Atlantic returned to near full-glacial conditions. The YDC vegetation patterns demonstrate (1) rapid ecological responsiveness to abrupt climate change and (2) spatially varied patterns of YDC climate change. (C) 2002 Elsevier Science Ltd. All rights reserved.
BibTeX: @article{Shuman2002a, author = {Shuman, B and Thompson, W and Bartlein, P and Williams, JW}, title = {The anatomy of a climatic oscillation: vegetation change in eastern North America during the Younger Dryas chronozone}, journal = {Quaternary Science Reviews}, year = {2002}, volume = {21}, number = {16-17}, pages = {1777--1791}, note = {http://geography.uoregon.edu/envchange/figures/Shuman-etal-QSR-2002a-figs/index.html} }
Solomon1992	Solomon, A. & Bartlein, P.	Past and future climate change - response by mixed deciduous coniferous forest ecosystems in northern Michigan [Abstract] [BibTeX]	1992	Canadian Journal of Forest Research Vol. 22 (11) , pp. 1727-1738	article
Abstract: During the 21st century, global climate change is expected to become a significant force redefining global biospheric boundaries and vegetation dynamics. In the northern hardwood - boreal forest transition forests, it should, at the least, control reproductive success and failure among unmanaged mixed forest stands. One means by which to predict future responses by the mixed forests is to examine the way in which they have responded to climate changes in the past. We used proxy climate data derived from Holocene (past 10 000 years) pollen records in the western Upper Peninsula of Michigan to drive forest gap models, in an effort to define regional prehistoric vegetation dynamics on differing soils. The gap models mimic forest reproduction and growth as a successional process and, hence, are appropriate for defining long-term tree and stand dynamics. The modeled period included a mid-postglacial period that was warmer than today's climate. Model failures, made apparent from the exercise, were corrected and the simulations were repeated until the model behaved credibly. Then, the same gap model was used to simulate potential future vegetation dynamics, driven by projections of a future climate that was controlled by greenhouse gases. This provided us with the same "measure" of vegetation in the past, present, and future, generating a continuously comparable record of change and stability in forest composition and density. The resulting projections of vegetation response to climate change appear to be affected more by the rate than by the magnitude of climate change.
BibTeX: @article{Solomon1992, author = {Solomon, AM and Bartlein, PJ}, title = {Past and future climate change - response by mixed deciduous coniferous forest ecosystems in northern Michigan}, journal = {Canadian Journal of Forest Research}, year = {1992}, volume = {22}, number = {11}, pages = {1727--1738} }
Steingisser2009	Steingisser, A. & Marcus, W.	Human Impacts on geyser basins [BibTeX] [PDF]	2009	Yellowstone Science Vol. 17 , pp. 1-18	article
BibTeX: @article{Steingisser2009, author = {Steingisser, A and Marcus, WA}, title = {Human Impacts on geyser basins}, journal = {Yellowstone Science}, year = {2009}, volume = {17}, pages = {1-18} }
Stoughton2000	Stoughton, J. & Marcus, W.	Persistent impacts of trace metals from mining on floodplain grass communities along Soda Butte Creek, Yellowstone National Park [Abstract] [BibTeX] [PDF]	2000	Environmental Management Vol. 25 (3) , pp. 305-320	article
Abstract: In Yellowstone National Park, tailings and associated trace metals from past mining have been deposited along 28 km of Soda Butte Creek by large flood events. This study documents grass species diversity, density, and biomass; trace metal concentrations in soils; and soil pH, salinity, and clay content in four selected floodplain meadows contaminated by these tailings. Trace metal levels frequently exceed acceptable concentrations for agricultural soils at sampling points within the meadows. pH levels within flood-deposited tailings are strongly to moderately acid, while pH levels outside of tailings deposits are neutral. The data analysis: (1) shows that metals and acidity associated with tailings affect plant biomass, density, and diversity; (2) documents that the vegetation/metal and vegetation/pH associations are more of a threshold than a linear relationship; and (3) suggests that other factors may be involved in structuring the community. Vegetation diversity, density, and biomass decrease at threshold levels of trace metal concentrations and soil pH in all four meadows. CuSum plots of diversity in relation to trace metal levels show a decrease in mean diversity at 315 ppm copper, 22 ppm arsenic, 4.2% iron, 65 ppm lead, and 170 ppm zinc. Densities of Phleum pratense and Poa pratensis were significantly lower(P less than or equal to 0.001) on plots with more than 250 ppm copper. Above-ground biomass of Phleum pratense was also significantly lower on plots with copper levels above 250 ppm. Decreased mean grass density was found on plots with pH < 6.4, but the only statistically significant difference was for Juncus balticus, which had increased density on plots with pH < 6.4. In contrast to the clear impacts of trace metals and pl-l on vegetation, other site characteristics did not alter measured vegetation characteristics.
BibTeX: @article{Stoughton2000, author = {Stoughton, JA and Marcus, WA}, title = {Persistent impacts of trace metals from mining on floodplain grass communities along Soda Butte Creek, Yellowstone National Park}, journal = {Environmental Management}, year = {2000}, volume = {25}, number = {3}, pages = {305--320} }
Tang2008	Tang, G. & Bartlein, P.	Simulating the climatic effects on vegetation: approaches, issues and challenges [Abstract] [BibTeX] [PDF]	2008	Progress in Physical Geography Vol. 32 (5) , pp. 543-556	article
Abstract: Vegetation modelling has been viewed as a major approach for examining the dynamics of vegetation under climatic change. However, the characterization of uncertainty of model results is still a key Issue. In order to improve future model-based research, it is important to synthesize the current approaches and the issues that arise in vegetation modelling and to propose potential strategies for improving model-based research. This study first reviews the progress of vegetation models from static-equilibrium to transient-dynamic and to current coupled multi-objective vegetation models. Then, the four main sources leading to the uncertainty of model results are described, including (1) factors related to vegetation models (their structure, assumption and parameterization), (2) the data used to run a model, (3) the approaches used to validate model results, and (4) the spatiotemporal scaling issues involved in vegetation modelling. Finally, four strategies are proposed for improving future model-based research. These include improvements in the model structure and parameterization, enhancement of the quality of analytical data, improvement of the analytical approaches, and continued development of coupled dynamic vegetation models. Using a literature synthesis, this study provides researchers with a general guidance on applying vegetation models for simulating the effects of climatic variations on terrestrial vegetation.
BibTeX: @article{Tang2008, author = {Tang, GP and Bartlein, PJ}, title = {Simulating the climatic effects on vegetation: approaches, issues and challenges}, journal = {Progress in Physical Geography}, year = {2008}, volume = {32}, number = {5}, pages = {543--556} }
Tang2009	Tang, G.; Shafer, S.; Bartlein, P. & Holman, J.	Effects of experimental protocol on global vegetation model accuracy: A comparison of simulated and observed vegetation patterns for Asia [Abstract] [BibTeX] [PDF]	2009	Ecological Modelling Vol. 220 (12) , pp. 1481-1491	article
Abstract: Prognostic vegetation models have been widely used to study the interactions between environmental change and biological systems. This study examines the sensitivity of vegetation model simulations to: (i) the selection of input climatologies representing different time periods and their associated atmospheric CO2, concentrations, (ii) the choice of observed vegetation data for evaluating the model results, and (iii) the methods used to compare simulated and observed vegetation. We use vegetation simulated for Asia by the equilibrium vegetation model BIOME4 as a typical example of vegetation model output. BIOME4 was run using 19 different climatologies and their associated atmospheric CO2 concentrations. The Kappa statistic, Fuzzy Kappa statistic and a newly developed map-comparison method, the Nomad index, were used to quantify the agreement between the biomes simulated under each scenario and the observed vegetation from three different global land- and tree-cover data sets: the global Potential Natural Vegetation data set (PNV), the Global Land Cover Characteristics data set (GLCC), and the Global Land Cover Facility data set (GLCF). The results indicate that the 30-year mean climatology (and its associated atmospheric CO2 concentration) for the time period immediately preceding the collection date of the observed vegetation data produce the most accurate vegetation simulations when compared with all three observed vegetation data sets. The study also indicates that the BIOME4-simulated vegetation for Asia more closely matches the PNV data than the other two observed vegetation data sets. Given the same observed data, the accuracy assessments of the BIOME4 simulations made using the Kappa, Fuzzy Kappa and Nomad index map-comparison methods agree well when the compared vegetation types consist of a large number of spatially continuous grid cells. The results of this analysis can assist model users in designing experimental protocols for simulating vegetation. (C) 2009 Elsevier B.V. All rights reserved.
BibTeX: @article{Tang2009, author = {Tang, GP and Shafer, SL and Bartlein, PJ and Holman, JO}, title = {Effects of experimental protocol on global vegetation model accuracy: A comparison of simulated and observed vegetation patterns for Asia}, journal = {Ecological Modelling}, year = {2009}, volume = {220}, number = {12}, pages = {1481--1491} }
Thompson2008	Thompson, R.; Anderson, K. & Bartlein, P.	Quantitative estimation of bioclimatic parameters from presence/absence vegetation data in North America by the modern analog technique [Abstract] [BibTeX] [PDF]	2008	Quaternary Science Reviews Vol. 27 (11-12) , pp. 1234-1254	article	modern climate analogues
Abstract: The method of modern analogs is widely used to obtain estimates of past climatic conditions from paleobiological assemblages, and despite its frequent use, this method involved so-far untested assumptions. We applied four analog approaches to a continental-scale set of bioclimatic and plant-distribution presence/absence data for North America to assess how well this method works under near-optimal modern conditions. For each point on the grid, we calculated the similarity between its vegetation assemblage and those of all other points on the grid (excluding nearby points). The climate of the points with the most similar vegetation was used to estimate the climate at the target grid point. Estimates based the use of the Jaccard similarity coefficient had smaller errors than those based on the use of a new similarity coefficient, although the latter may be more robust because it does not assume that the "fossil" assemblage is complete. The results of these analyses indicate that presence/absence vegetation assemblages provide a valid basis for estimating bioclimates on the continental scale. However, the accuracy of the estimates is strongly tied to the number of species in the target assemblage, and the analog method is necessarily constrained to produce estimates that fall within the range of observed values. We applied the four modern analog approaches and the mutual overlap (or "mutual climatic range") method to estimate bioclimatic conditions represented by the plant macrofossil assemblage from a packrat midden of Last Glacial Maximum age from southern Nevada. In general, the estimation approaches produced similar results in regard to moisture conditions, but there was a greater range of estimates for growing-degree days. Despite its limitations, the modern analog technique can provide paleoclimatic reconstructions that serve as the starting point to the interpretation of past climatic conditions. Published by Elsevier Ltd.
BibTeX: @article{Thompson2008, author = {Thompson, RS and Anderson, KH and Bartlein, PJ}, title = {Quantitative estimation of bioclimatic parameters from presence/absence vegetation data in North America by the modern analog technique}, journal = {Quaternary Science Reviews}, year = {2008}, volume = {27}, number = {11-12}, pages = {1234--1254} }
Thompson1999	Thompson, R.; Anderson, K. & PJ, B.	Atlas of Relations Between Climatic Parameters and Distributions of Important Trees and Shrubs in North America [BibTeX] [Figures]	1999		techreport	vegetation and climate
BibTeX: @techreport{Thompson1999, author = {Thompson, RS and Anderson, KH and Bartlein PJ}, title = {Atlas of Relations Between Climatic Parameters and Distributions of Important Trees and Shrubs in North America}, year = {1999}, note = {http://pubs.usgs.gov/pp/p1650-a/} }
Thompson1998	Thompson, R.; Hostetler, S.; Bartlein, P. & Anderson, K.	A Strategy for Assessing Potential Future Changes in Climate, Hydrology, and Vegetation in the Western United States [BibTeX] [Figures]	1998	(1153)	techreport	future vegetation change
BibTeX: @techreport{Thompson1998, author = {Thompson, RS and Hostetler, SW and Bartlein, PJ and Anderson, KH}, title = {A Strategy for Assessing Potential Future Changes in Climate, Hydrology, and Vegetation in the Western United States}, year = {1998}, number = {1153}, note = {http://geography.uoregon.edu/envchange/figures/circular/index.html} }
Thompson2004	Thompson, R.; Shafer, S.; Anderson, K.; Strickland, L.; Pelltier, R.; Bartlein, P. & Kerwin, M.	Topographic, bioclimatic, and vegetation characteristics of three ecoregion classification systems in North America: Comparisons along continent-wide transects [Abstract] [BibTeX] [PDF]	2004	Environmental Management Vol. 34 , pp. S125-S148-S125-S148	article	vegetation and climate
Abstract: Ecoregion classification systems are increasingly used for policy and management decisions, particularly among conservation and natural resource managers. A number of ecoregion classification systems are currently available, with each system defining ecoregions using different classification methods and different types of data. As a result, each classification system describes a unique set of ecoregions. To help potential users choose the most appropriate ecoregion system for their particular application, we used three latitudinal transects across North America to compare the boundaries and environmental characteristics of three ecoregion classification systems [Kuchler, World Wildlife Fund (WWF), and Bailey]. A variety of variables were used to evaluate the three systems, including woody plant species richness, normalized difference in vegetation index (NDVI), and bioclimatic variables (e.g., mean temperature of the coldest month) along each transect. Our results are dominated by geographic patterns in temperature, which are generally aligned north-south, and in moisture, which are generally aligned east-west. In the west, the dramatic changes in physiography, climate, and vegetation impose stronger controls on ecoregion boundaries than in the east. The Kuchler system has the greatest number of ecoregions on all three transects, but does not necessarily have the highest degree of internal consistency within its ecoregions with regard to the bioclimatic and species richness data. In general, the WWF system appears to track climatic and floristic variables the best of the three systems, but not in all regions on all transects.
BibTeX: @article{Thompson2004, author = {Thompson, RS and Shafer, SL and Anderson, KH and Strickland, LE and Pelltier, RT and Bartlein, PJ and Kerwin, MW}, title = {Topographic, bioclimatic, and vegetation characteristics of three ecoregion classification systems in North America: Comparisons along continent-wide transects}, journal = {Environmental Management}, year = {2004}, volume = {34}, pages = {S125-S148--S125-S148} }
Vanniere2011	Vanniere, B.; Power, M.; Roberts, N.; Tinner, W.; Carrion, J.; Magny, M.; Bartlein, P.; Colombaroli, D.; Daniau, A.; Finsinger, W.; Gil-Romera, G.; Kaltenrieder, P.; Pini, R.; Sadori, L.; Turner, R.; Valsecchi, V. & Vescovi, E.	Circum-Mediterranean fire activity and climate changes during the mid-Holocene environmental transition (8500-2500 cal. BP) [Abstract] [BibTeX]	2011	Holocene Vol. 21 (1) , pp. 53-73	article
Abstract: A mid- to late-Holocene synthesis of fire activity from the Mediterranean basin explores the linkages among fire, climate variability and seasonality through several climatic and ecological transitions. Regional fire histories were created from 36 radiocarbon-dated sedimentary charcoal records, available from the Global Charcoal Database. During the mid-Holocene 'Thermal Maximum' around 7500-4500 cal. BP, charcoal records from the northern Mediterranean suggest an increase in fire while records from the southern Mediterranean indicate a decrease associated with wetter-than-present summers. A North-South partition between 40 degrees and 43 degrees N latitude is apparent in the central and western Mediterranean. Relatively abrupt changes in fire activity are observed c. 5500-5000 cal. BP. Records of Holocene fire activity appear sensitive to both orbitally forced climate changes and shorter-lived excursions which may be related to North Atlantic cold events, possibly modulated by an NAO-like climate mechanism. In cases where human-fire interactions have been documented, the regional coherency between fire occurrence and climate forcing suggests a dominant fire-climate relationship during the early-mid Holocene. The human influence on regional fire activity became increasingly important after c. 4000-3000 cal. BP. Results also suggest that: (1) teleconnections between the Mediterranean area and other climatic regions, in particular the North Atlantic and the low latitudes monsoon areas, influenced past fire activity; (2) gradual forcing, such as changes in orbital parameters, may have triggered abrupt shifts in fire activity; (3) regional fire reconstructions contradict former notions of a gradual (mid-to late-Holocene) aridification of the entire region due to climate and/or human activities and the importance of shorter-term events; (4) Mediterranean fire activity appears hightly sensitive to climate dynamics and thus could be considerably impacted by future climate changes.
BibTeX: @article{Vanniere2011, author = {Vanniere, B and Power, MJ and Roberts, N and Tinner, W and Carrion, J and Magny, M and Bartlein, P and Colombaroli, D and Daniau, AL and Finsinger, W and Gil-Romera, G and Kaltenrieder, P and Pini, R and Sadori, L and Turner, R and Valsecchi, V and Vescovi, E}, title = {Circum-Mediterranean fire activity and climate changes during the mid-Holocene environmental transition (8500-2500 cal. BP)}, journal = {Holocene}, year = {2011}, volume = {21}, number = {1}, pages = {53--73} }
Vassiljev1994	Vassiljev, J.; Harrison, S.; Hostetler, S. & Bartlein, P.	Simulation of long-term thermal-characteristics of 3 Estonian lakes [Abstract] [BibTeX]	1994	Journal of Hydrology Vol. 163 (1-2) , pp. 107-123	article
Abstract: A one-dimensional surface energy-balance lake model, coupled to a thermodynamic model of lake ice, is used to simulate variations in the temperature of and evaporation from three Estonian lakes: Karujarv, Viljandi and Kirjaku. The model is driven by daily climate data, derived by cubic-spline interpolation from monthly mean data, and was run for periods of 8 years (Kirjaku) up to 30 years (Viljandi). Simulated surface water temperature is in good agreement with observations: mean differences between simulated and observed temperatures are from -0.8-degrees-C to + 0.1-degrees-C. The simulated duration of snow and ice cover is comparable with observed. However, the model generally underpredicts ice thickness and overpredicts snow depth. Sensitivity analyses suggest that the model results are robust across a wide range (0.1-2.0 m-1) of lake extinction coefficient: surface temperature differs by less than 0.5-degrees-C between extreme values of the extinction coefficient. The model results are more sensitive to snow and ice albedos. However, changing the snow (0.2-0.9) and ice (0.15-0.55) albedos within realistic ranges does not improve the simulations of snow depth and ice thickness. The underestimation of ice thickness is correlated with the overestimation of snow cover, since a thick snow layer insulates the ice and limits ice formation. The overestimation of snow cover results from the assumption that all the simulated winter precipitation occurs as snow, a direct consequence of using daily climate data derived by interpolation from mean monthly data.
BibTeX: @article{Vassiljev1994, author = {Vassiljev, J and Harrison, SP and Hostetler, S and Bartlein, PJ}, title = {Simulation of long-term thermal-characteristics of 3 Estonian lakes}, journal = {Journal of Hydrology}, year = {1994}, volume = {163}, number = {1-2}, pages = {107--123} }
Walsh2010	Walsh, M.; Pearl, C.; Whitlock, C.; Bartlein, P. & Worona, M.	An 11 000-year-long record of fire and vegetation history at Beaver Lake, Oregon, central Willamette Valley [Abstract] [BibTeX] [PDF]	2010	Quaternary Science Reviews Vol. 29 (9-10) , pp. 1093-1106	article
Abstract: High-resolution macroscopic charcoal and pollen analysis were used to reconstruct an 11 000-year-long record of fire and vegetation history from Beaver Lake, Oregon, the first complete Holocene paleoecological record from the floor of the Willamette Valley. In the early Holocene (ca 11 000-7500 calendar years before present [cal yr BP]), warmer, drier summers than at present led to the establishment of xeric woodland of Quercus, Corylus, and Pseudotsuga near the site. Disturbances (i.e., floods, fires) were common at this time and as a result Alnus rubra grew nearby. High fire frequency occurred in the early Holocene from ca 11 200-9300 cal yr BP. Riparian forest and wet prairie developed in the middle Holocene (ca 7500 cal yr BP), likely the result of a decrease in the frequency of flooding and a shift to effectively cooler, wetter conditions than before. The vegetation at Beaver Lake remained generally unchanged into the late Holocene (from 4000 cal yr BP to present), with the exception of land clearance associated with Euro-American settlement of the valley (ca 160 cal yr BP). Middle-to-late Holocene increases in fire frequency, coupled with abrupt shifts in fire-episode magnitude and charcoal composition, likely indicate the influence anthropogenic burning near the site. The paleoecological record from Beaver Lake, and in particular the general increase in fire frequency over the last 8500 years, differs significantly from other low-elevation sites in the Pacific Northwest, which suggests that local controls (e.g., shifts in vegetation structure, intensification of human land-use), rather than regional climatic controls, more strongly influenced its environmental history. (C) 2010 Elsevier Ltd. All rights reserved.
BibTeX: @article{Walsh2010, author = {Walsh, MK and Pearl, CA and Whitlock, C and Bartlein, PJ and Worona, MA}, title = {An 11 000-year-long record of fire and vegetation history at Beaver Lake, Oregon, central Willamette Valley}, journal = {Quaternary Science Reviews}, year = {2010}, volume = {29}, number = {9-10}, pages = {1093--1106} }
Walsh2010a	Walsh, M.; Whitlock, C. & Bartlein, P.	1200 years of fire and vegetation history in the Willamette Valley, Oregon and Washington, reconstructed using high-resolution macroscopic charcoal and pollen analysis [Abstract] [BibTeX] [PDF]	2010	Palaeogeography Palaeoclimatology Palaeoecology Vol. 297 (2) , pp. 273-289	article
Abstract: High-resolution macroscopic charcoal and pollen analyses were used to reconstruct the fire and vegetation history of the Willamette Valley for the last 1200 years. Presented in this paper are three new paleoecological reconstructions from lake Oswego, Porter Lake, and Warner Lake, Oregon, and portions of previous reconstructions from Battle Ground lake, Washington, and Beaver Lake, Oregon. The reconstructions show that prior to Euro-American settlement vegetation and fire regimes were influenced by a combination of natural and anthropogenic factors. Battle Ground Lake shows a stronger influence from climate, while Lake Oswego, Beaver Lake, Porter Lake, and Warner Lake were more controlled by human activity. However, human-set fires were also modulated by regional climate variability during the Medieval Climate Anomaly and the Little Ice Age. Fire reconstructions from Battle Ground Lake, Lake Oswego, Beaver Lake, and Porter Lake imply that fires were infrequent in the Willamette Valley 200-300 years prior to Euro-American settlement. The decline of Native American populations due to introduced disease may have led to this reduction in fire activity. The prehistoric record from Warner Lake, however, indicates that fires in the foothills of the Cascade Range were more frequent than on the valley floor, at least until ca. AD 1800. The historic portions of the reconstructions indicate that Euro-American land clearance for agriculture and logging produced the most dramatic shifts in vegetation and fire regimes. All five records indicate that few fires in the Willamette Valley have occurred since ca. AD 1930, and fires today are predominantly grass fires. (C) 2010 Elsevier B.V. All rights reserved.
BibTeX: @article{Walsh2010a, author = {Walsh, MK and Whitlock, C and Bartlein, PJ}, title = {1200 years of fire and vegetation history in the Willamette Valley, Oregon and Washington, reconstructed using high-resolution macroscopic charcoal and pollen analysis}, journal = {Palaeogeography Palaeoclimatology Palaeoecology}, year = {2010}, volume = {297}, number = {2}, pages = {273--289} }
Walsh2008	Walsh, M.; Whitlock, C. & Bartlein, P.	A 14,300-year-long record of fire-vegetation-climate linkages at Battle Ground Lake, southwestern Washington [Abstract] [BibTeX] [PDF]	2008	Quaternary Research Vol. 70 (2) , pp. 251-264	article
Abstract: High-resolution macroscopic charcoal analysis was used to reconstruct a 14,300-year-long Fire history record from the lower Columbia River Valley in southwestern Washington, which was compared to a previous vegetation reconstruction for the site. In the late-glacial period (ca. 14,300-13,100 cal yr BP), Pinus/Picea-dominated parkland supported little to no fire activity. From the late-glacial to the early Holocene (ca. 13,100-10,800 cal yr BP), Pseudotsuga/Abies-dominated forest featured more frequent fire episodes that burned mostly woody vegetation. In the early to middle Holocene (ca. 10,800-5200 cal yr BP), Quercus-dominated savanna was associated with frequent fire episodes of low-to-moderate severity, with art increased herbaceous (i.e., grass) charcoal content. From the middle to late Holocene (ca. 5200 cal yr BP to present), forest dominated by Pseudotsuga, Thuja-type, and Tsuga heterophylla supported less frequent, but mostly large or high-severity fire episodes. Fire episodes were least frequent, but were largest or most severe, after ca. 2500 cal yr BP. The fire history at Battle Ground Lake was apparently driven by climate, directly through the length and severity of the fire season, and indirectly through climate-driven vegetation shifts, which affected available fuel biomass. (C) 2008 University of Washington. All rights reserved.
BibTeX: @article{Walsh2008, author = {Walsh, MK and Whitlock, C and Bartlein, PJ}, title = {A 14,300-year-long record of fire-vegetation-climate linkages at Battle Ground Lake, southwestern Washington}, journal = {Quaternary Research}, year = {2008}, volume = {70}, number = {2}, pages = {251--264} }
Webb1998	Webb, T.; Anderson, K.; Bartlein, P. & Webb, R.	Late Quaternary climate change in eastern North America: A comparison of pollen-derived estimates with climate model results [Abstract] [BibTeX]	1998	Quaternary Science Reviews Vol. 17 (6-7) , pp. 587-606	article
Abstract: Late Quaternary pollen data from eastern North America and pollen-climate response surfaces provide tests of the climate simulations from Version 1 of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM1) for 21, 16, 14, 11, and 6 ka. The model results are also compared to those from Version 0 of the NCAR model (CCM0). In contrast to CCM0, CCM1 used a slab ocean model to compute sea surface temperatures, included a seasonal cycle, and computed soil moisture. It also used an improved set of boundary conditions from 21 to 6 ka. In eastern North America, CCM 1 simulated lower temperatures at the last glacial maximum (LGM) 21,000 years ago than did CCM0 and therefore was in better agreement with the pollen data than the CCM0 simulations were. The simulations by CCM 1 for mean July temperatures from 16 to 11 ka, however, were much higher than those by CCM0 and were higher than present for much of the area south of the Laurentide ice sheet. These simulated conditions differ markedly from those reconstructed from the pollen data, which indicate July temperatures significantly lower than present from 16 to 11 ka. At 6 ka, CCM 1 simulated climate conditions similar to today and therefore not too different from those simulated by CCM0 or those inferred from the pollen data. For 6 Era in the upper Midwest, however, CCM1 simulated moisture conditions similar to present, which is an improvement over CCM0. However, the new simulation still does not match the drier-than-present conditions inferred from the pollen data. Derailed analysis of the circulation variables and the surface-energy-budget terms simulated by CCM1 show that both dynamic and thermodynamic factors contributed to the major discrepancy in July temperatures from 16 to 11 ka. The simulated glacial anticyclone created less cloudiness and rainfall south of the ice sheet, and these conditions allowed the increased summertime insolation from 16 to 11 ka to overheat the surface. The impact of the ice sheet on model dynamics therefore led to overestimation of summer temperatures south of the ice for this time period. (C) 1998 Elsevier Science Ltd. All rights reserved.
BibTeX: @article{Webb1998, author = {Webb, T and Anderson, KH and Bartlein, PJ and Webb, RS}, title = {Late Quaternary climate change in eastern North America: A comparison of pollen-derived estimates with climate model results}, journal = {Quaternary Science Reviews}, year = {1998}, volume = {17}, number = {6-7}, pages = {587--606} }
Webb1992	Webb, T. & Bartlein, P.	Global changes during the last 3 million years - climatic controls and biotic responses [BibTeX] [PDF]	1992	Annual Review of Ecology and Systematics Vol. 23 , pp. 141-173	article
BibTeX: @article{Webb1992, author = {Webb, T and Bartlein, PJ}, title = {Global changes during the last 3 million years - climatic controls and biotic responses}, journal = {Annual Review of Ecology and Systematics}, year = {1992}, volume = {23}, pages = {141--173} }
Whitlock2004a	Whitlock, C. & Bartlein, P. Gillespie, A.; Porter, S. & Atwater, B. (Hrsg.)	Holocene fire activity as a record of past environmental change ( The Quaternary Period in the United States ) [BibTeX] [PDF]	2004	The Quaternary Period in the United States , pp. 479-490	inbook
BibTeX: @inbook{Whitlock2004a, author = {Whitlock, C and Bartlein, PJ}, title = {The Quaternary Period in the United States}, publisher = {Elsevier, Amsterdam}, year = {2004}, pages = {479-490} }
Whitlock1997	Whitlock, C. & Bartlein, P.	Vegetation and climate change in northwest America during the past 125 kyr [Abstract] [BibTeX] [Figures] [PDF]	1997	Nature Vol. 388 (6637) , pp. 57-61	article	paleoclimatology and paleoecology
Abstract: Vegetation records spanning the past 21 kyr in western North America display spatial patterns of change that reflect the influence of variations in the large-scale controls of climate(1). Among these controls are millennial-scale variations in the seasonal cycle of insolation and the size of the ice sheet, which affect regional climates directly through changes in temperature and net radiation, and indirectly by shifting atmospheric circulation. Longer vegetation records provide an opportunity to examine the regional response to different combinations of these large-scale controls, and whether non-climatic controls are important. But most of the longer North American records(2,3) are of insufficient quality to allow a robust test, and the Long European records(4-9) are in regions where the vegetation response to climate is often difficult to separate from the response to ecological and anthropogenic controls. Here we present a 125-kyr record of vegetation and climate change for the forest/steppe border of the eastern Cascade Range, northwest America. Pollen data disclose alternations of forest and steppe that are consistent with variations in summer insolation and global ice-volume, and vegetational transitions correlate well with the marine isotope-stage boundaries. The close relationship between vegetation and climate beyond the Last Glacial Maximum provides evidence that climate variations are the primary cause of regional vegetation change on millennial timescales, and that non-climatic controls are secondary.
BibTeX: @article{Whitlock1997, author = {Whitlock, C and Bartlein, PJ}, title = {Vegetation and climate change in northwest America during the past 125 kyr}, journal = {Nature}, year = {1997}, volume = {388}, number = {6637}, pages = {57--61}, note = {http://geography.uoregon.edu/envchange/figures/Whitlock-and-Bartlein-Nature-1997-figs/nature.htm} }
Whitlock1993	Whitlock, C. & Bartlein, P.	Spatial variations of Holocene climatic change in the Yellowstone Region [BibTeX] [PDF]	1993	Quaternary Research Vol. 39 (2) , pp. 231-238	article	paleoclimatology
BibTeX: @article{Whitlock1993, author = {Whitlock, C and Bartlein, PJ}, title = {Spatial variations of Holocene climatic change in the Yellowstone Region}, journal = {Quaternary Research}, year = {1993}, volume = {39}, number = {2}, pages = {231--238} }
Whitlock2001	Whitlock, C.; Bartlein, P.; Markgraf, V. & Ashworth, A. Markgraf, V. (Hrsg.)	The Mid-latitudes of North and South America During the Last Glacial Maximum and Early Holocene: Similar Paleoclimatic Sequences Despite Differing Large-Scale Controls ( Interhemispheric Climate Linkages in the Americas and their Societal Effects ) [BibTeX] [Figures]	2001	Interhemispheric Climate Linkages in the Americas and their Societal Effects , pp. 391-416	inbook	paleoclimatic analysis and data-model comparisons
BibTeX: @inbook{Whitlock2001, author = {Whitlock, C and Bartlein, PJ and Markgraf, V and Ashworth, AC}, title = {Interhemispheric Climate Linkages in the Americas and their Societal Effects}, publisher = {Academic Press}, year = {2001}, pages = {391-416}, note = {http://geography.uoregon.edu/envchange/figures/Whitlock-etal-IHCL-2001-figs/index.html} }
Whitlock2003	Whitlock, C.; Bartlein, P.; Marlon, J.; Brunelle, A. & Long, C.	Holocene fire reconstructions from the northwestern U.S.: an examination at multiple time scales [BibTeX] [PDF]	2003	5th Symposium on Fire and Forest Meteorology. American Meteorological Society , pp. 4C.1-1 - 4C.1-5	inproceedings	fire: paleo and modern
BibTeX: @inproceedings{Whitlock2003, author = {Whitlock, C and Bartlein, PJ and Marlon, J and Brunelle, A and Long, C.}, title = {Holocene fire reconstructions from the northwestern U.S.: an examination at multiple time scales}, booktitle = {5th Symposium on Fire and Forest Meteorology. American Meteorological Society}, year = {2003}, pages = {4C.1-1 - 4C.1-5} }
Whitlock1995	Whitlock, C.; Bartlein, P. & Van Norman, K.	Stability of Holocene climate regimes in the Yellowstone region [Abstract] [BibTeX] [PDF]	1995	Quaternary Research Vol. 43 (3) , pp. 433-436	article	paleoclimatology
Abstract: A 12,500-yr pollen record from Loon Lake, Wyoming provides information on the climate history of the southwestern margin of Yellowstone National Park. The environmental reconstruction was used to evaluate hypotheses that address spatial variations in the Holocene climate of mountainous regions. Loon Lake lies within the summer-dry/winter-wet climate regime. An increase in xerophytic pollen taxa suggests drier-than-present conditions between ca. 9500 and 5500 C-14 yr B.P. This response is consistent with the hypothesis that increased summer radiation and the expansion of the east Pacific subtropical high-pressure system in the early Holocene intensified summer drought at locations within the summer-dry/winter-wet regime. This climate history contrasts with that of nearby sites in the summer-wet/winter-dry region, which were under the influence of stronger summer monsoonal circulation in the early Holocene. The Loon Lake record implies that the location of contrasting climate regimes did not change in the Yellowstone region during the Holocene. The amplitude of the regimes, however, was determined by the intensity of circulation features and these varied with temporal changes in the seasonal distribution of solar radiation. (C) 1995 University of Washington.
BibTeX: @article{Whitlock1995, author = {Whitlock, C and Bartlein, PJ and Van Norman, KJ}, title = {Stability of Holocene climate regimes in the Yellowstone region}, journal = {Quaternary Research}, year = {1995}, volume = {43}, number = {3}, pages = {433--436} }
Whitlock2006	Whitlock, C.; Bianchi, M.; Bartlein, P.; Markgraf, V.; Marlon, J.; Walsh, M. & McCoy, N.	Postglacial vegetation, climate, and fire history along the east side of the Andes (lat 41-42.5 degrees S), Argentina [Abstract] [BibTeX]	2006	Quaternary Research Vol. 66 (2) , pp. 187-201	article
Abstract: The history of the low-elevation forest and forest-steppe ecotone on the east side of the Andes is revealed in pollen and charcoal records obtained from mid-latitude lakes. Prior to 15,000 cat yr BP, the vegetation was characterized by steppe vegetation with isolated stands of Nothofagus. The climate was generally dry, and the sparse vegetation apparently lacked sufficient fuels to burn extensively. After 15,000 cat yr BP, a mixture of Nothofagus forest and shrubland/steppe developed. Fire activity increased between 13,250 and 11,400 cat yr BP, contemporaneous with a regionally defined cold dry period (Huelmo/Maseardi Cold Reversal). The early-Holocene period was characterized by an open Nothofagus forest/shrubland mosaic, and fire frequency was high in dry sites and low in wet sites; the data suggest a sharp decrease in moisture eastward from the Andes. A shift to a surface-fire regime occurred at 7500 cat yr BP at the wet site and at 4400 cat yr BP at the dry site, preceding the expansion of Austrocedrus by 1000-1500 yr. The spread of Austrocedrus is explained by a shift towards a cooler and wetter climate in the middle and late Holocene. The change to a surface-fire regime is consistent with increased interannual climate variability and the onset or strengthening of ENSO. The present-day mixed forest dominated by Nothofagus and Austrocedrus was established in the last few millennia. (c) 2006 University of Washington. All rights reserved.
BibTeX: @article{Whitlock2006, author = {Whitlock, C and Bianchi, MM and Bartlein, PJ and Markgraf, V and Marlon, J and Walsh, M and McCoy, N}, title = {Postglacial vegetation, climate, and fire history along the east side of the Andes (lat 41-42.5 degrees S), Argentina}, journal = {Quaternary Research}, year = {2006}, volume = {66}, number = {2}, pages = {187--201} }
Whitlock2008	Whitlock, C.; Marlon, J.; Briles, C.; Brunelle, A.; Long, C. & Bartlein, P.	Long-term relations among fire, fuel, and climate in the north-western US based on lake-sediment studies [Abstract] [BibTeX]	2008	International Journal of Wildland Fire Vol. 17 (1) , pp. 72-83	article
Abstract: Pollen and high-resolution charcoal records from the north-western USA provide an opportunity to examine the linkages among fire, climate, and fuels on multiple temporal and spatial scales. The data suggest that general charcoal levels were low in the late-glacial period and increased steadily through the last 11 000 years with increasing fuel biomass. At local scales, fire occurrence is governed by the interaction of site controls, including vegetation, local climate and fire weather, and topography. At subregional scales, patterns in the long term fire-episode frequency data are apparent: The Coast Range had relatively few fires in the Holocene, whereas the Klamath-Siskiyou region experienced frequent fire episodes. Fire regimes in the northern Rocky Mountains have been strongly governed by millennial- and centennial-scale climate variability and regional differences in summer moisture. At regional scales, sites in present-day summer-dry areas show a period of protracted high fire activity within the early Holocene that is attributed to intensified summer drought in the summer-dry region. Sites in summer-wet areas show the opposite pattern, that fire was lower in frequency than present in the early Holocene as result of strengthened monsoonal circulation then. Higher fire-episode frequency at many sites in the last 2000 years is attributed to greater drought during the Medieval Climate Anomaly and possibly anthropogenic burning. The association between drought, increased fire occurrence, and available fuels evident on several time scales suggests that long-term fire history patterns should be considered in current assessments of historical fire regimes and fuel conditions.
BibTeX: @article{Whitlock2008, author = {Whitlock, C and Marlon, J and Briles, C and Brunelle, A and Long, C and Bartlein, P}, title = {Long-term relations among fire, fuel, and climate in the north-western US based on lake-sediment studies}, journal = {International Journal of Wildland Fire}, year = {2008}, volume = {17}, number = {1}, pages = {72--83} }
Whitlock2007	Whitlock, C.; Moreno, P. & Bartlein, P.	Climatic controls of Holocene fire patterns in southern South America [Abstract] [BibTeX]	2007	Quaternary Research Vol. 68 (1) , pp. 28-36	article
Abstract: Holocene fire-climate-vegetation linkages are mostly understood at individual sites by comparing charcoal and pollen records with other paleoenvironmental proxy and model simulations. This scale of reconstruction often obscures detection of large-scale patterns in past fire activity that are related to changes in regional climate and vegetation. A network of 31 charcoal records from southern South America was examined to assess fire history along a transect from subtropic to subantarctic biomes. The charcoal data indicate that fire activity was greater than present at ca. 12,000 cal yr BP and increased further and was widespread at 9500 cal yr BR Fire activity decreased and became more spatially variable by 6000 cal yr BP, and this trend continued to present. Atmospheric circulation anomalies during recent high-fire years show a southward shift in westerlies, and paleoclimate model simulations and data syntheses suggest that such conditions may have prevailed for millennia in the early Holocene when the pole-to-equator temperature gradients were weaker and annual temperatures were higher than present, in response to orbitaltime-scale insolation changes. (c) 2007 University of Washington. All rights reserved.
BibTeX: @article{Whitlock2007, author = {Whitlock, C and Moreno, PI and Bartlein, P}, title = {Climatic controls of Holocene fire patterns in southern South America}, journal = {Quaternary Research}, year = {2007}, volume = {68}, number = {1}, pages = {28--36} }
Whitlock2000	Whitlock, C.; Sarna-Wojcicki, A.; Bartlein, P. & Nickmann, R.	Environmental history and tephrostratigraphy at Carp Lake, southwestern Columbia Basin, Washington, USA [Abstract] [BibTeX] [Figures] [PDF]	2000	Palaeogeography Palaeoclimatology Palaeoecology Vol. 155 (1-2) , pp. 7-29	article	paleoclimatology and paleoecology
Abstract: Sediment cores from Carp Lake provide a pollen record of the last ca. 125,000 years that helps disclose vegetational and climatic conditions from the present day to the previous interglaciation (120-133 ka). The core also contained 15 tephra layers, which were characterised by electron-microprobe analysis of volcanic glass shards. Identified tephra include Mount St. Helens Ye, 3.69 ka; Mazama ash bed, 7.54 ka; Mount St, Helens layer C, 35-50 ka; an unnamed Mount St. Helens tephra, 75-150 ka; the tephra equivalent of layer E at Pringle Falls, Oregon, <218 ka; and an andesitic tephra layer similar to that at Tulelake, California, 174 ka, Ten calibrated radiocarbon ages and the ages of Mount St. Helens Ye, Mazama ash, and the unnamed Mount St, Helens tephra were used to develop an age-depth model. This model was refined by also incorporating the age of marine oxygen isotope stage (IS) boundary 4/5 (73.9 ka) and the age of IS-Se (125 ka). The justification for this age-model is based on an analysis of the pollen record and lithologic data. The pollen record is divided into 11 assemblage zones that describe alternations between periods of montane conifer forest, pine forest, and steppe. The previous interglacial period (IS-5e) supported temperate xerothermic forests of pine and oak and a northward and westward expansion of steppe and juniper woodland, compared to their present occurrence. The period from 83 to 117 ka contains intervals of pine forest and parkland alternating with pine-spruce forest, suggesting shifts from cold humid to cool temperate conditions. Between 73 and 83 ka, a forest of oak, hemlock, Douglas-fir, and fir was present that has no modem analogue. It suggests warm wet summers and cool wet winters. Cool humid conditions during the mid-Wisconsin interval supported mixed conifer forest with Douglas-fir and spruce. The glacial interval featured cold dry steppe, with an expansion of spruce in the late-glacial. Xerothermic communities prevailed in the early Holocene, when temperate steppe was widespread and the lake dried intermittently. The middle Holocene was characterised by ponderosa pine forest, and the modern vegetation was established in the last 3900 yr, when ponderosa pine, Douglas-fir, fir, and oak were part of the local vegetation. (C) 2000 Elsevier Science B.V. All rights reserved.
BibTeX: @article{Whitlock2000, author = {Whitlock, C and Sarna-Wojcicki, AM and Bartlein, PJ and Nickmann, RJ}, title = {Environmental history and tephrostratigraphy at Carp Lake, southwestern Columbia Basin, Washington, USA}, journal = {Palaeogeography Palaeoclimatology Palaeoecology}, year = {2000}, volume = {155}, number = {1-2}, pages = {7--29}, note = {http://geography.uoregon.edu/envchange/figures/Whitlock-etal-P3-2000-figs/index.html} }
Whitlock2004	Whitlock, C.; Skinner, C.; Bartlein, P.; Minckley, T. & Mohr, J.	Comparison of charcoal and tree-ring records of recent fires in the eastern Klamath Mountains, California, USA [Abstract] [BibTeX] [PDF]	2004	Canadian Journal of Forest Research Vol. 34 (10) , pp. 2110-2121	article
Abstract: Fire-history reconstructions are based on tree-ring records that span the last few centuries and charcoal data from lake-sediment cores that extend back several thousand years. The two approaches have unique strengths and weaknesses in their ability to depict past fire events and fire regimes, and most comparisons of these datasets in western conifer forests have focused on sites characterized by high-severity crown fires. Tree-ring and charcoal data spanning the last 300 years in four watersheds in the montane forests of the Klamath Mountains provided an opportunity to compare the records in a fire regime of frequent low- to moderate-severity surface events. The charcoal data were obtained from small lakes, and tree-ring records were derived from fire-scar chronologies at multiple sites within each watershed. The comparison indicates that the tree-ring records detected individual fires not evident in the lake-sediment profiles, whereas the charcoal data disclosed variations in fuel loading and general levels of burning at broader spatial scales. Regional burning in the late 19th and early 20th centuries was evident in the lake-sediment records, and both datasets registered a decline in fire activity in the late 20th century. Thus, the two types of data provide complementary as well as supplementary information on past fire conditions.
BibTeX: @article{Whitlock2004, author = {Whitlock, C and Skinner, CN and Bartlein, PJ and Minckley, T and Mohr, JA}, title = {Comparison of charcoal and tree-ring records of recent fires in the eastern Klamath Mountains, California, USA}, journal = {Canadian Journal of Forest Research}, year = {2004}, volume = {34}, number = {10}, pages = {2110--2121} }
Whitmore2005	Whitmore, J.; Gajewski, K.; Sawada, M.; Williams, J.; Shuman, B.; Bartlein, P.; Minckley, T.; Viau, A.; Webb, T.; Shafer, S.; Anderson, P. & Brubaker, L.	Modern pollen data from North American and Greenland for multi-scale paleoenvironmental applications [Abstract] [BibTeX] [PDF]	2005	Quaternary Science Reviews Vol. 24 (16-17) , pp. 1828-1848	article	vegetation and climate
Abstract: The modern pollen network in North America and Greenland is presented as a database for use in quantitative calibration studies and paleoenvironmental reconstructions. The georeferenced database includes 4634 samples from all regions of the continent and 134 pollen taxa that range from ubiquitous to regionally diagnostic taxa. Climate data and vegetation characteristics were assigned to every site. Automated and manual procedures were used to verify the accuracy of geographic coordinates and identify duplicate records among datasets, incomplete pollen sums, and other potential errors. Data are currently available for almost all of North America, with variable density. Pollen taxonomic diversity, as measured by the Shannon-Weiner coefficient, varies as a function of location, as some vegetation regions are dominated by one or two major pollen producers, while other regions have a more even composition of pollen taxa. Squared-chord distances computed between samples show that most modern pollen samples find analogues within their own vegetation zone. Both temperature and precipitation inferred from best analogues are highly correlated with observed values but temperature exhibits the strongest relation. Maps of the contemporary distribution of several pollen types in relation to the range of the plant taxon illustrate the correspondence between plant and pollen ranges. (c) 2005 Elsevier Ltd. All rights reserved.
BibTeX: @article{Whitmore2005, author = {Whitmore, J and Gajewski, K and Sawada, M and Williams, JW and Shuman, B and Bartlein, PJ and Minckley, T and Viau, AE and Webb, T and Shafer, S and Anderson, P and Brubaker, L}, title = {Modern pollen data from North American and Greenland for multi-scale paleoenvironmental applications}, journal = {Quaternary Science Reviews}, year = {2005}, volume = {24}, number = {16-17}, pages = {1828--1848} }
Williams2009	Williams, J.; Shuman, B. & Bartlein, P.	Rapid responses of the prairie-forest ecotone to early Holocene aridity in mid-continental North America [Abstract] [BibTeX] [PDF]	2009	Global and Planetary Change Vol. 66 (3-4) , pp. 195-207	article	paleoecology and paleoclimatology
Abstract: The prairie-forest transition in midcontinental North America is a major physiognomic boundary, and its shifts during the Holocene are a classic example of climate-driven ecotonal dynamics. Recent work suggests asymmetrical Holocene behavior, with a relatively rapid early Holocene deforestation and more gradual reforestation later in the Holocene. This paper presents a new synthesis of the Holocene history of the Great Plains prairie-forest ecotone in the north-central US and central Canada that updates prior mapping efforts and systematically assesses rates of change. Changes in percent woody cover (%WC) are inferred from fossil pollen records, using the modern analog technique and surface-sediment pollen samples cross-referenced against remotely sensed observations. For contemporary pollen samples from the Great Plains, %WC linearly correlates to percent arboreal pollen (%AP), but regression parameters vary interregionally. At present, %AP is consistently higher than %WC, because of high background levels of arboreal pollen. Holocene maps of the eastern prairie-forest ecotone agree with prior maps, showing a rapid decrease in %WC and eastward prairie advance between 10,000 and 8000 ka (1 ka = 1000 calibrated years before present), a maximum eastward position of the ecotone from 7 to 6 ka, and increased %WC and westward prairie retreat after 6 ka. Ecotone position is ambiguous in Iowa and southeastern Minnesota, due to a scarcity of modern analogs for early-Holocene samples with high Minus abundances and for samples from alluvial sediments. The northern prairie-forest ecotone was positioned in central Saskatchewan between 12 and 10 ka, stabilized from 10 to 6 ka despite decreases in %WC at some sites, then moved south after 6 ka. In both east and north. ecotonal movements are consistent with a dry early Holocene and increasing moisture availability after 6 ka. Sites near the ecotone consistently show an asymmetric pattern of abrupt early Holocene deforestation (<300 years) and gradual reforestation after 6 ka. Early Holocene decreases in %WC are faster than the corresponding drops in %AP, because the analog-based %WC reconstructions correct for the high background levels of arboreal pollen types that blur temporal variations in %AP. For example, at Elk Like. the %AP decline lasts 1000 years, whereas the %WC decline occurs between adjacent pollen samples, approximately 300 years apart. Thus, early Holocene deforestation may have been even more abrupt than previously recognized. Rapid deforestation likely was promoted both by rapid climate changes around 8.2 ka and positive fire-vegetation feedbacks. Non-linear vegetational responses to hydrological variability are consistent with 1) other paleorecords showing rapid die-offs of some eastern tree species in response to aridity and 2) observations of threshold-type ecological responses to recent climate events. The 21st-century trajectory for the Great Plains prairie-forest ecotone is uncertain, because climate models differ over the direction of regional precipitation trends. but future drying would be more likely to trigger threshold-type shifts in ecotone position. (c) 2008 Elsevier B.V. All rights reserved.
BibTeX: @article{Williams2009, author = {Williams, JW and Shuman, B and Bartlein, PJ}, title = {Rapid responses of the prairie-forest ecotone to early Holocene aridity in mid-continental North America}, journal = {Global and Planetary Change}, year = {2009}, volume = {66}, number = {3-4}, pages = {195--207} }
Williams2010	Williams, J.; Shuman, B.; Bartlein, P.; Diffenbaugh, N. & Webb, T.	Rapid, time-transgressive, and variable responses to early Holocene midcontinental drying in North America [Abstract] [BibTeX] [PDF]	2010	Geology Vol. 38 (2) , pp. 135-138	article	paleoecology and paleoclimatology
Abstract: The end Pleistocene to early Holocene drying of the North American midcontinent is an important case study for understanding regional drought, its drivers, and its impacts. This paper synthesizes pollen, delta C-13, eolian, and paleohydrological proxies to document the spatial and temporal patterns in the onset and rate of drying. The timing of onset ranged from 14 to 6 ka with most sites drying between 10 and 8 ka (calendar years ago). The dominant spatial pattern is time transgressive, with interior Great Plains sites beginning to dry before peripheral sites. This time-transgressive trend can be explained as a region-wide drying that caused ecotones to shift eastward, or could indicate a progressive shift in atmospheric drying from west to east. One-third of sites responded rapidly to drying; a cluster of rapid responses occurred ca. 8 ka. The combination of onsets between 14 and 6 ka and rapid responses at 8 ka strongly suggests that (1) the combination of high summer insolation, Laurentide Ice Sheet retreat, and Lake Agassiz drainage drove midcontinental drying, and (2) drying accelerated with Laurentide Ice Sheet collapse at 8.4 ka. Local factors strongly mediate the timing and rate of site responses to regional drying. Local responses to future drying in the Great Plains also should be highly variable, which challenges impact assessments of future climate changes.
BibTeX: @article{Williams2010, author = {Williams, JW and Shuman, B and Bartlein, PJ and Diffenbaugh, NS and Webb, T}, title = {Rapid, time-transgressive, and variable responses to early Holocene midcontinental drying in North America}, journal = {Geology}, year = {2010}, volume = {38}, number = {2}, pages = {135--138} }
Williams2004	Williams, J.; Shuman, B.; Webb, T.; Bartlein, P. & Leduc, P.	Late-Quaternary vegetation dynamics in North America: Scaling from taxa to biomes [Abstract] [BibTeX] [PDF]	2004	Ecological Monographs Vol. 74 (2) , pp. 309-334	article	paleoecology and paleoclimatology
Abstract: This paper integrates recent efforts to map the distribution of biomes for the late Quaternary with the detailed evidence that plant species have responded individualistically to climate change at millennial timescales. Using a fossil-pollen data set of over 700 sites, we review late-Quaternary vegetation history in northern and eastern North America across levels of ecological organization from individual taxa to biomes, and apply the insights gained from this review to critically examine the biome maps generated from the pollen data. Higher-order features of the vegetation (e.g., plant associations, physiognomy) emerge from individualistic responses of plant taxa to climate change, and different representations of vegetation history reveal different aspects of vegetation dynamics. Vegetation distribution and composition were relatively stable during full-glacial times (2100017 000 yr BP) [calendar years] and during the mid- to late Holocene (7000-500 yr BP), but changed rapidly during the late-glacial period and early Holocene (16000-.8000 yr BP) and after 500 yr BP Shifts in plant taxon distributions were characterized by individualistic changes in population abundances and ranges and included large east-west shifts in distribution in addition to the northward redistribution of most taxa. Modern associations such as Fagus-Tsuga and Picea-Alnus-Betula date to the early Holocene, whereas other associations common to the late-glacial period (e.g., Picea-Cyperaceae-Fraxinus-Ostrya/ Carpinus). no longer exist. Biomes are dynamic entities that have changed in distribution, composition; and structure over time. The late-Pleistocene suite of biomes is distinct from those that grew during the Holocene. The pollen-based biome reconstructions are able to capture the major features of late-Quaternary vegetation but downplay the magnitude and variety of vegetational responses to climate change by (1) limiting, apparent land-cover change to ecotones, (2) masking internal variations in biome composition, and (3) obscuring the range shifts and changes in abundance among individual taxa. The compositional and structural differences between full-glacial and recent biomes of the same type are. similar to or greater than the spatial heterogeneity in the composition and structure of present-day biomes. This spatial and temporal heterogeneity allows biome maps to accommodate individualistic behavior among species but masks climatically important variations in taxonomic composition as well as structural differences between modern biomes and their ancient counterparts.
BibTeX: @article{Williams2004, author = {Williams, JW and Shuman, BN and Webb, T and Bartlein, PJ and Leduc, PL}, title = {Late-Quaternary vegetation dynamics in North America: Scaling from taxa to biomes}, journal = {Ecological Monographs}, year = {2004}, volume = {74}, number = {2}, pages = {309--334} }
Williams2000	Williams, J.; Webb, T.; Shurman, B. & Bartlein, P.	Do low CO2 concentrations affect pollen-based reconstructions of LGM climates? A response to "Physiological significance of low atmospheric CO2 for plant-climate interactions" by Cowling and Sykes [BibTeX] [PDF]	2000	Quaternary Research Vol. 53 (3) , pp. 402-404	article	vegetation and climate
BibTeX: @article{Williams2000, author = {Williams, JW and Webb, T and Shurman, BN and Bartlein, PJ}, title = {Do low CO2 concentrations affect pollen-based reconstructions of LGM climates? A response to "Physiological significance of low atmospheric CO2 for plant-climate interactions" by Cowling and Sykes}, journal = {Quaternary Research}, year = {2000}, volume = {53}, number = {3}, pages = {402--404} }
Wright2000	Wright, A.; Marcus, W. & Aspinall, R.	Evaluation of multispectral, fine scale digital imagery as a tool for mapping stream morphology [Abstract] [BibTeX]	2000	Geomorphology Vol. 33 (1-2) , pp. 107-120	article
Abstract: Multispectral digital imagery acquired from Soda Butte and Cache Creeks, Montana and Wyoming was used in conjunction with field data to classify and map hydrogeomorphic stream units on four stream reaches. The morphologic units that were field mapped were eddy drop zones, glides, low gradient riffles, high gradient riffles, lateral scour pools, attached bars, detached bars, and large woody debris. Unsupervised and supervised classifications of the imagery were used to develop a Maximum Joint Probability classification and an Alternative Joint Probability classification of the stream reaches. The Maximum Joint Probability classification allowed only one of the image classes to represent each hydrogeomorphic unit on the field map and resulted in relatively low overall accuracies for identification of these units of 10% to 50%. The Alternative Joint Probability classification allowed each image class to represent any geomorphic unit where the probability of a correct classification was greater than random. In this technique, two or three image classes were assigned to represent each hydrogeomorphic unit, resulting in higher overall accuracies of 28% to 80%. Accurate classification of hydrogeomorphic units was hampered by poor rectification of imagery with the field maps because of inadequate ground control points. In general, the largest hydrogeomorphic units were most accurately classified, whereas units that were small in area or spatially linear were least likely to be accurately classified. The results of this study demonstrated that multispectral digital imagery has the potential to be a useful tool for mapping hydrogeomorphic stream units at fine scales. Imagery to be an effective tool, however, careful measures such as accurate documentation of ground control points must be taken to ensure accurate rectification of the imagery with field maps. (C) 2000 Elsevier Science B.V. All rights reserved.
BibTeX: @article{Wright2000, author = {Wright, A and Marcus, WA and Aspinall, R}, title = {Evaluation of multispectral, fine scale digital imagery as a tool for mapping stream morphology}, journal = {Geomorphology}, year = {2000}, volume = {33}, number = {1-2}, pages = {107--120} }

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