Boundaries

This ecoregion covers inland basins of central-southern Oregon, a small part of northeastern California, and parts of northwestern Nevada. These desert basins are largely defined by alkaline lakes.

Topography

The basins of this ecoregion represent an extension of the Basin and Range province that lies between the Cascade Mountains to the west and the Owyhee Upland to the east. The landscape is characterized by a pattern of basins and raised terraces, with uplift areas of grabens and horsts that run in a north-south orientation (Minckley et al. 1986).

Freshwater habitats

The freshwater habitats include alkaline lakes, wetlands, playas, and isolated springs and streams (Anderson et al. 1997).

Terrestrial habitats

The dominant vegetation in the ecoregion is sagebrush (Artemisia spp.), typically associated with various wheatgrasses (Agropyron spp.), Idaho fescue (Festuca idahoensis) or other perennial bunchgrasses (Franklin and Dyrness 1988).

Description of endemic fishes

Endemic fish include the Borax Lake chub (Gila boraxobius), a dwarf species found in Borax Lake, Lower Borax Lake, and associated ponds and marshes, and the Warner sucker (Catostomus warnerensis), found in ephemeral lakes, sloughs, lower-gradient streams, and three permanent lakes in the Warner Basin in Oregon and Nevada (Sigler & Sigler 1994; Williams 1995a; Williams 1995b).

Justification for delineation

Ecoregion boundaries are taken from Abell et al. (2000) and are based on subregions defined by Maxwell et al. (1995). Modifications to the boundaries of this ecoregion were based on a biogeographic assessment performed by The Nature Conservancy. The boundaries were modified to include the watersheds of Massacre Lake and Madeline Plains, previously in the Lahontan [126] ecoregion, as well as Surprise Valley watershed, portions of which were in both the Lahontan [126] and Sacramento-San Joaquin [125] ecoregions.