Ecoregions demarcate areas of similar characteristics in ecosystems and in the type, quality, and quantity of natural resources. The purpose of ecoregions is to provide a spatial map for research assessment, management, and monitoring of ecosystems and their components. State agencies are a primary user of data. With the help of bioregion data, state agencies develop biological criteria and water quality standards. Ecoregions ultimately are a management tool that federal and state agencies can use to integrate their plans. The ecoregions defined in the maps are based on the premise that ecological regions can be identified through the analysis of the patterns and composition of biotic and abiotic components. In addition, these components reflect the differences in ecosystem quality and integrity.
1. Coast Range
Highly productive, rain-drenched coniferous forests cover the low mountains of the Coast Range. Douglas firs are prevalent on the intensively logged and managed landscape.
Coast Range Photo by Catalena Cabrera1a. The Coastal Lowlands ecoregion encompasses estuarine marshes, freshwater lakes, black-water streams, marine terraces, and sand dunes area. Elevations range from sea level to 300 feet. Channelization and diking have converted many of its wetlands into dairy pastures; associated stream quality degradation has occurred.
1b. The Coastal Uplands ecoregion extends to an elevation of about 500 feet. The climate of the Coastal Uplands ecoregion is marine-influenced with an extended winter rainy season, enough fog during the summer dry season to reduce vegetal moisture stress, and a lack of seasonal temperature extremes. The ecoregion roughly corresponds with the historic distribution of Sitka spruce. The extent of the original forest has been greatly reduced by logging.
1d. The Volcanics ecoregion varies in elevation from 1000 to 4000 feet and is disjunct. Columnar and pillow basalt outcrops occur. Its mountains may have been offshore seamounts engulfed by continental sediments about 200 million years ago. The basaltic substrate preserves relatively stable summer stream flows that still support spring Chinook salmon and summer steelhead. Its forests are intensively managed.
1g. The Mid-Coastal Sedimentary ecoregion is commonly underlain by massive beds of siltstone and sandstone. Its dissected, forested mountains are very rugged and are prone to mass movement when the vegetal cover is removed. Stream gradients and fluvial erosion rates can be high.
3. Willamette Valley
Rolling prairies, deciduous/coniferous forests, and extensive wetlands characterized the pre-settlement landscape of this broad, lowland valley.The Willamette Valley ecoregion is distinguished from the adjacent Coast Range (1) and Cascades (4) ecoregions by lower precipitation, less relief, and a different mosaic of vegetation. Landforms consist of terraces and floodplains, interlaced and surrounded by rolling hills. Productive soils and a temperate climate make it one of the most important agricultural areas in Oregon.
Farmland in Willamette Valley Photo by Catalena Cabrera3b. In the Willamette River and Tributaries Gallery Forest ecoregion, meandering, low-gradient channels and oxbow lakes are incised into broad floodplains. Deciduous riparian forests that once grew on its fertile, alluvial soils have been largely replaced by agriculture and rural residential, suburban, and urban development.
3c. The undulating Prairie Terraces ecoregion is dissected by low-gradient, meandering streams and rivers. Its fluvial terraces once supported prairie and oak woodlands which were maintained by burning; Oregon ash and Douglas fir occurred in wetter areas. Today, grass seed and grain crops are commonly grown.
3d. The Valley Foothills ecoregion is a transitional zone between the Willamette Valley (3), the Cascades (4), and the Coast Range (1). It has less rainfall than adjacent, more mountainous ecoregions and, consequently, its potential natural vegetation is distinct. Oregon white oak and Douglas fir were originally dominant but, today, rural residential development, woodland, pastureland, vineyards, tree farms, and orchards are common.
4. Cascades
This mountainous ecoregion underlain by Cenozoic volcanics has been affected by alpine glaciations. It is characterized by steep ridges and river valleys in the west, a high plateau in the east, and both active and dormant volcanoes. Elevations range upwards to 14,410 feet. Its moist, temperate climate supports an extensive and highly productive coniferous forest. Subalpine meadows occur at high elevations.
Cascades Photo by Catalena Cabrera4a. The Western Cascades Lowlands and Valleys ecoregion is characterized by a network of steep ridges and narrow valleys. Elevations are generally less than 3,200 feet and are the lowest in the Cascades ecoregion. The wet, mild climate promotes lush forests that are dominated by Douglas fir and western hemlock. It is one of the most important timber producing areas in the Northwest.
4b. The Western Cascades Montane Highlands ecoregion is composed of steep, glaciated mountains that have been dissected by high-gradient streams. It has lower temperatures than Ecoregion 4a and is characterized by a deep annual snow pack. Soils are of the frigid and cryic temperature regimes and support forests dominated by Pacific silver fir, western hemlock, mountain hemlock, Douglas fir, and noble fir.
4c. The Cascade Crest Montane Forest ecoregion consists of an undulating plateau punctuated by volcanic buttes and cones that reach a maximum elevation of about 6,500 feet. Its Pliocene and Pleistocene volcanics were glaciated leaving numerous lakes in their wake. The ecoregion is extensively forested with mountain hemlock and Pacific silver fir.
4d. The Cascades Subalpine/Alpine ecoregion is an area of high, glaciated, volcanic peaks that rise above subalpine meadows. Elevations range from 5,600 to 12,000 feet. Active glaciation occurs on the highest volcanoes and decreases from north to south. The winters are very cold and the growing season is extremely short. Flora and fauna adapted to high elevations include herbaceous and shrubby subalpine meadow vegetation and scattered patches of mountain hemlock, subalpine fir, and whitebark pine.
4f. The Umpqua Cascades ecoregion is a transitional zone between the lusher and moister forests of Ecoregions 4a and 4b to the north. Vegetation is a mix of grand fir, white fir, western hemlock, Pacific silver fir, and Douglas fir with Shasta red fir also occurring and increasing to the south. Vegetation diversity is greater than in Ecoregions 4a and 4b, which have cooler summers.
Text after: David E. Pater (Ecoregions of Western Washington and Oregon, 1998)
Pater, David E. et al, Ecoregions of Western Washington and Oregon, USGS/USEPA, Denver, CO., 1998. Lane Council of Governments, 125 E. 8th Ave., Eugene, OR 97401 (541) 682-4283. Tobys, Robert and Catalena Cabrera, Cartographers, Spring 1998.
