Sagebrush Ecosystems
Sagebrush ecosystems are located throughout the Great Basin, but they are considered by many to be an endangered ecosystem due to invasive species proliferation (particularly cheatgrass [Bromus tectorum]), alternations of fire regimes, and land conversion and uses (e.g., urbanization, dryland farming, overgrazing). The peril face by the sagebrush ecosystem has been brought to light by its namesake species—sage grouse (Centrocercus urophasianus), whose populations have declined to the point of being considered a threatened species because of loss of habitat.
Section 1: Geographic Distribution
Geographic Location
Sagebrush steppe is located throughout the regions of the Intermountain West, the Columbia and Colorado Plateaus, and the Great Basin in the states of Washington, Oregon, California, Idaho, Nevada, Wyoming, Utah, Colorado, Arizona, and New Mexico (figure 8.1).
Section 2: Major Land Resource Areas of Sagebrush Ecosystems
Sagebrush ecosystems are present in varying extents and densities throughout the following Major Land Resource Areas (MLRAs):
- Region B-7 Columbia Basin
- Region B-8 Columbia Plateau
- Region B-10 Central Rocky and Blue Mountain Foothills
- Region B-11 Snake River Plains
Sagebrush is present in Regions B-12 Lost River Valleys and Mountains and B-13 Eastern Idaho Plateaus, but these areas are dominated by bunchgrass, grass, and forb species.
- Region D-23 Malheur High Plateau
- Region D-24 Humboldt Area
- Region D-25 Owyhee High Plateau
- Region D-26 Carson Basin and Mountains
- Region D-32 Northern Intermountain Desertic Basins
- Region D-34A Cool Central Desertic Basin and Plateaus (higher precipitation)
- Region D-35 Colorado Plateau (sagebrush and pinyon-juniper)
- Region D-36 Southwestern Plateaus, Mesas, and Foothills (sagebrush and pinyon-juniper)
Each MLRA has reflective physiography, geology, climate, water, soil and biological resources, and associated land uses. There is a great degree of variation across the MLRAs of sagebrush ecosystems in terms of climate, topography, soil, plant species composition, hydrology, and community dynamics. This text will look at each system through an MLRA lens. To find out more information about specific MLRAs, the US Department of Agriculture Handbook 296, Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin, is available online, as well as interactive MLRA maps.
B-Region MLRAs
This region comprises plains and plateaus across 81,225 square miles of Idaho, Washington, Oregon, and a small area of Utah, on the leeward side of the Cascade Mountains (figure 8.2). The topography of the region ranges from smooth, rolling plain dissected by rivers and streams to steep slopes, and young incised valleys. Alluvial fans of glacial washout are prevalent in some northern areas. The formation of the area’s topography and soils were heavily influenced by Missoulian floods. Soils across the region are dominantly and mo