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This mountainous ecoregion stretches from the central portion of western Washington, through the spine of Oregon, and includes a disjunct area in northern California. It is underlain by Cenozoic volcanics and much of the region has been affected by alpine glaciation. In Oregon and Washington, the western Cascades are older, lower, and dissected by numerous, steep-sided stream valleys. A high plateau occurs to the east, with both active and dormant volcanoes. Some peaks reach over 14,000 feet. Soils are mostly of cryic and frigid temperature regimes, with some mesic soils at low elevations and in the south. Andisols and Inceptisols are common. The Cascades have a moist, temperate climate that supports an extensive and highly productive coniferous forest that is intensively managed for logging. At lower elevations in the north, Douglas-fir, western hemlock, western red cedar, big leaf maple, and red alder are typical. At higher elevations, Pacific silver fir, mountain hemlock, subalpine fir, noble fir, and lodgepole pine occur. In southern Oregon and California, more incense cedar, white fir, and Shasta red fir occur along with other Sierran species. Subalpine meadows and rocky alpine zones occur at highest elevations. (USEPA 2013)









Land Use/Human Activities



US Environmental Protection Agency. 2013. Primary distinguishing characteristics of level iii ecoregions of the continental united states.