Pacific Northwest South Central Southeast S. Appalachians Southwest Biophysical Site Description

Elevations range from 1,300 to 4,000 feet. Temperatures range between extremes of hot summers and cold winters that are typical of a continental climate. Precipitation increases from west (12 in.) to east (24 in.). Two-thirds of the precipitation occurs during the growing season. Soils vary, but are generally aridicols in the west and mollisols in the east. Soils in the northern Great Plains, west of the Missouri River in the Dakotas, northwestern Nebraska, northeastern Wyoming and Montana are formed from sandstone and shales. These soils range from clayey, fine-loamy, to fine silty soils of mixed origin in level and hilly-undulating lands with major contributions from loess, eolian sand, alluvium, and mountain outwash. Vegetation Description This vegetation type is characterized by the dominance of cool-season grasses such as western wheatgrass and needlegrasses. Warm-season grasses like grama grasses and buffalo grass are common and usually increase in dominance following heavy disturbance. Needleleaf sedge is very common throughout this vegetation type, especially in sandy soils. Needleleaf sedge tends to be very drought-resistant. Disturbance Description The northern mixed-grass prairie is strongly influenced by wet-dry cycles. Fire, grazing by large ungulates and small mammals such as prairie dogs and soil disturbances (i.e. buffalo wallows and prairie dog towns