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Shrub-steppe is a type of low rainfall natural grassland. While arid, shrub-steppes have sufficient moisture to support a cover of perennial grasses and/or shrubs, a feature which distinguishes them from deserts.

The primary ecological processes historically at work in shrub-steppe ecosystems are drought and fire. Shrub-steppe plant species have developed particular adaptations to low annual precipitation and summer drought conditions. Plant adaptations to landscape differences in soil moisture regimes influences their distribution. A frequent fire regime in the shrub-steppe similarly adds to the patchwork pattern of shrub and grass that characterizes shrub steppe ecosystems.[1]

North America[edit]

Sagebrush steppe in northeastern Nevada along US 93
Shrubsteppe, one of America's most endangered ecosystems on fire. Artemisia tridentata ssp. wyomingensis is not adapted to fire unlike Ponderosa pine and is in most cases completely destroyed.

The shrub steppes of North America occur in the western United States and western Canada, in the rainshadow zone between the Cascades, and Sierra Nevada on the west, and the Rocky Mountains on the east. They extend from south-central British Columbia down into southeastern Washington state, eastern Oregon, and eastern California, and across through Idaho, Nevada, and Utah into western Wyoming and Colorado, and down into northern and central New Mexico and northern Arizona. Growth is dominated by primarily low-lying shrubs, such as big sagebrush- Artemisia tridentata, and Purshia tridentata with too low of rainfall to support the growth of trees, though trees do occur. Other important plants are Bunchgrass- Pseudoroegneria spicata which have historically provided forage for livestock as well as wildlife, but are quickly being replaced by non-native annual species like Cheatgrass- Bromus tectorum, tumble mustard- Sisymbrium altissimum, and Russian thistle- Salsola kali. There is also a suite of animals that call the shrubsteppe home including Sage Grouse, Pygmy rabbit, Western rattlesnake, Pronghorn.

Historically much of the shrubsteppe in Washington State was referred to as "scabland" because of the deep channels cut into pure basalt rock by cataclysmic floods more than 10,000 years ago Channeled Scablands. Major threats to the ecosystem include overgrazing, fires, invasion by non-native species, development since much of it is at lower elevations and conversion to cropland, as well as energy development. Less than 50% of Washington State's historic shrubsteppe remains [2] and according to some estimates it is only 12 to 15% [3].

Shrub-steppe ecoregions of North America include:


  1. ^ "Shrub-Steppe Ecosystem". Ecosystems. Washington Native Plant Society.
  2. ^ "Shrubsteppe Ecology". Washington Department of Fish and Wildlife.
  3. ^ "Threats to the Shrub-Steppe". Washington Native Plant Society.
  4. ^ "Great Basin shrub steppe". Terrestrial Ecoregions. World Wildlife Fund.
  5. ^ "Snake-Columbia shrub steppe". Terrestrial Ecoregions. World Wildlife Fund.
  6. ^ "Wyoming Basin shrub steppe". Terrestrial Ecoregions. World Wildlife Fund.

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