Canyon Grasslands and Associated Shrublands of West-central Idaho and Adjacent Areas

Grasslands dominated by perennial bunchgrasses occupy the canyon-like valleys of the Snake and Salmon Rivers and their tributaries in west-central Idaho. The grassland areas differ in elevation from 215 to 2400 m. (710-7800 feet) with slopes commonly of 45 to 70 percent and ranging to over 100 percent. Soils, mainly Xerolls, derived from volcanic materials are permeable and relatively stable. Vertical zonation of climate, vegetation and soils prevails, modified mainly by differences in aspect. Plant communities (series) characterized by Agropyron spicatum, Festuca idahoensis and Carex hoodii respectively, occupy most of the grassland area and form five habitat types. Minor types of less certain seral status occur at low elevations and are dominated by Sporobolus cryptandrus and Aristida longiseta. Small inclusions of shrub grass types are dominated by Artemisia rigida, Symphoricarpos albus, Rhus glabra, Cercocarpus ledifolius and Celtis reticulata. Vegetation altered by the effects of livestock grazing in the century of white settlement shows extensive loss of native species and replacement by aliens, mainly of Mediterranean origin. Principal invaders were Bromus tectorum and other annual bromes, but others, including several species of Centaurea, are increasing on depleted sites