18 – Wyoming Basin (4 – level 4 ecoregions)

“This ecoregion is a broad intermontane basin interrupted by hills and low mountains and dominated by arid grasslands and shrublands. Nearly surrounded by forest covered mountains, the region is somewhat drier than the Northwestern Great Plains (43) to the northeast and does not have the extensive cover of pinyon-juniper woodland found in the Colorado Plateaus (20) to the south. Much of the region is used for livestock grazing, although many areas lack sufficient vegetation to support this activity. The region contains major producing natural gas and petroleum fields. The Wyoming Basin also has extensive coal deposits along with areas of trona, bentonite, clay, and uranium mining. (USGS, 2006; US EPA, 2013)”

18a – Rolling sagebrush steppe

• Topography -The semiarid Rolling Sagebrush Steppe is a vast region of rolling plains, alluvial and outwash fans, hills, cuestas, mesas, and terraces. This region is less hilly than the Foothill Shrublands and Low Mountains (18d) ecoregion.

• Land Use - Land use is mainly rangeland, with some areas of cropland along the Yampa River in hay, wheat, barley, or oats. Oil, gas, and coal deposits are scattered throughout the region.

• Soils -

• Vegetation - The sagebrush steppe natural vegetation includes western wheatgrass, needle-and-thread, blue grama, Sandberg bluegrass, Junegrass, rabbitbrush, fringed sage, Wyoming big sagebrush, silver and black sagebrush in lowlands, and mountain big sagebrush in the higher elevations.

• Other - Annual precipitation of 10 to 20 inches varies with elevation and proximity to mountains.

Sites to Visit - Axial Basin, Browns Park National Wildlife Refuge, Cedar Mountain, Elkhead Reservoir State Park, Irish Canyon, Morgan Bottoms, Sandwash Basin, Yampa River State Park
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18d – Foothill shrublands and low mountains

• Topography -The Foothill Shrublands and Low Mountains ecoregion includes isolated dry mountain ranges and foothill slopes, and in Colorado includes Cold Spring Mountain, Bishop Peak, Diamond Peak, and Lookout Mountain. The topography of this region is more rugged than the Rolling Sagebrush Steppe (18a).

• Land Use - Land use is mostly rangeland and wildlife habitat.

• Soils - Tertiary sedimentary rocks of sandstone and conglomerate are extensive, but shale, siltstone, and limestone also occur.

• Vegetation - Big sagebrush, rabbitbrush, pricklypear, bluebunch wheatgrass, and Idaho fescue dominate on fine-textured soils; Rocky Mountain juniper, Utah juniper, and mountain mahogany woodlands occur on rock outcrops.

• Other – A

Sites to Visit - Talamantes Creek, Vermillion Dry Creek
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18f – Laramie basin

• Topography -The Laramie Basin ecoregion is a wide intermontane valley of Wyoming that extends slightly into northern Colorado.

• Land Use - The rolling, high elevation valley of grass and shrubland is used primarily for seasonal livestock grazing. Some hay is produced along the Laramie River.

• Soils -

• Vegetation - For the region as a whole, natural vegetation is mainly grassland compared to the sagebrush steppe in other regions of Ecoregion 18. Needle-and-thread, western wheatgrass, blue grama, Indian ricegrass, and other mixed grass species are typical, along with rabbitbrush, fringed sage, and various forb and shrub species.

• Other - Elevations in the Colorado portion are generally 7800 to 9100 feet, with annual precipitation of 15 to 20 inches.

Sites to Visit - Laramie River
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18e – Salt desert shrub basins

• Topography - The arid Salt Desert Shrub Basins ecoregion includes disjunct playas and isolated sand dunes.

• Land Use - Land use is rangeland and wildlife habitat.

• Soils - The plains, terraces, and rolling alluvial fans of Ecoregion 18e have soils that tend to be more alkaline and less permeable than soils in the Rolling Sagebrush Steppe (18a).

• Vegetation - Vegetation is a sparse cover of arid land shrubs such as shadscale, greasewood, and Gardner's saltbush, with some areas of big sagebrush. Areas with stabilized sand dunes are dominated by alkali cordgrass, Indian ricegrass, blowout grass, alkali wildrye, and needle-and-thread.

• Other - This arid region is sensitive to grazing pressure, which may promote the invasion of weeds such as Russian thistle, cheatgrass, and the toxic halogeton.

Sites to Visit - Little Snake River, Powder Wash, Sand Wash
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