Boundaries

This ecoregion covers southeastern Colorado, northeastern New Mexico, most of southern Kansas, western Oklahoma, and the panhandle of Texas. It is largely defined by the watersheds of three rivers—the upper portions of the Arkansas, the South Canadian, and the upper half of the Red.

Topography

The ecoregion lies primarily within the Great Plains, but also a portion lies within the Rocky Mountains physiographic province. Elevation ranges from 144 m to over 4000 m on peaks along the western border.

Freshwater habitats

One distinctive feature of this semiarid region is the presence of heavily used aquifers, such as the famous Ogalalla Aquifer and the Arbuckle-Simpson Aquifer. The latter is relatively undeveloped, but critical subterranean and spring ecosystems in the area are threatened by pumping. Another important freshwater ecosystem is the Cheyenne Bottoms Wetland. This is the largest system of permanent and ephemeral wetlands left in the state of Kansas. It serves not only as a critical habitat for aquatic species, it also functions as a stopover point for more than half the population of northward-migrating shorebirds of North America (U.S. Environmental Protection Agency 1995; The Nature Conservancy 1996a).

Terrestrial habitats

As one travels west to east vegetation grades from montane forests in the Rockies through short and mixed grasslands, and then to mixed forest-grassland mosaics at the border of the Ozarks. A majority of the ecoregion is grassland, with characteristic species including grama (Bouteloua spp.), buffalo grass (Buchloe dactyloides), little bluestem (Schyzachrium scoparium) and western wheatgrass (Agropyron smithii) (Ricketts et al. 1999).

Description of endemic fishes

This ecoregion is not distinguished by particularly high endemism, with two endemic crayfish and two endemic fish. The fish are the prairie chub (Macrhybopsis australis) and peppered chub (Macrhybopsis tetranema).  

Justification for delineation

Ecoregion boundaries are taken from Abell et al. (2000) and are based on subregions defined by Maxwell et al. (1995).