Modeling Regions

Overview

This modeling region encompasses the Cascades province in Oregon and California. Along the western slope of the Cascade Range in Oregon, lower-elevation forest dominated by Douglas-fir and western hemlock gives way to Pacific silver fir at mid-elevations, and to mountain hemlock and subalpine vegetation at higher elevations. In the southern part of the range, moist lowland vegetation yields to drier, mixed-conifer forest. Historical fire frequencies range from low to high along a north-to-south moisture gradient. About two-thirds of the province in Oregon is administered by federal agencies. The Eastern Cascades are dominated by mixed-conifer and ponderosa pine forest at lower- to mid-elevations, and by true fir and mountain hemlock at higher elevations. Forest productivity is low in places owing to poor soils and high elevations. Historical fire frequencies were high, and fire suppression practices have resulted in areas with significant accumulations of fuel, and shifts in species composition and stand structure. About two-thirds of the area is federally managed. Forests of the California Cascades are dominated by mixed-conifer and pine forest in fire-adapted community types. Slightly less than half of the province is federally managed. Forests are fragmented as a result of fire, harvest activities, and checkerboard ownership patterns of Forest Service land.