Shrub-steppe

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.

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.

North America

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 [1] and according to some estimates it is only 12 to 15% [2].

Shrub-steppe ecoregions of North America include:

  • Great Basin shrub steppe: sagebrush steppe in eastern California, central Nevada, western Utah, and southeastern Idaho.
  • Mojave Desert sky island sagebrush steppe: the Mojave sky islands (with pinyon-juniper woodland) in southeastern California; and small portions of southern Nevada, southwestern Utah, and northwestern Arizona.
  • Colorado Plateau shrublands: western Colorado, northern and central New Mexico, northern Arizona, and eastern Utah
  • Eastern Cascades shrub steppe (including the Columbia Basin): in south-central Washington state, eastern Oregon, northeastern California, northern Nevada, and Idaho.
  • Wyoming Basin shrub steppe: in central Wyoming, reaching into south-central Montana, northeastern Utah, southwestern Idaho, and northwestern Colorado.
  • Okanagan shrub steppe: in the Okanagan Valley in south-central British Columbia, and the southern Similkameen Valley in south-central British Columbia and north-central Washington state.

References

  1. ↑ Shrubsteppe Ecology from Washington Department of Fish and Wildlife
  2. ↑ Threats to the Shrub-Steppe from WNPS

See also

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.