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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

124: Oregon Lakes

Major Habitat Type:

xeric freshwaters and endorheic (closed) basins

Author:

Text modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC, USA.

Countries:

United States

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.

Drainages flowing into:

This ecoregion includes closed drainage systems that do not flow outward into any rivers or oceans.

Main rivers or other water bodies:

Large lakes include Goose Lake, which straddles the California-Oregon border, and Lake Abert, Summer Lake, and Harney Lake in Oregon. There are numerous smaller lakes, several of which are far more important to the ecoregion’s biological distinctiveness.

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).

Climate:

This ecoregion is high desert and falls largely in the rain shadow of the Cascade Mountains. It receives little precipitation, averaging around 254 in annually (Anderson et al. 1997).

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).

Fish Fauna:

This ecoregion, like other desert areas, has low numbers of freshwater species and endemism, with just over twenty native fish species.

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).

Other noteworthy aquatic biotic elements:

This Great Basin ecoregion also includes a number of restricted-range freshwater mollusks, including the turban pebblesnail (Fluminicola turbiniformis), which is dependent upon oligotrophic springs. Known endemic snails associated with the alkaline lakes of this ecoregion include the lamb rams-horn (Planorbella oregonensis) and Harney Lake springsnail (Pyrgulopsis hendersoni). There are likely others as well (Frest & Johannes 1995).

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.

References/sources:

Abell, R., Olson, D., et al. (2000). "Freshwater ecoregions of North America" Washington, D.C.: Island Press.

Franklin, Jerry F. (1988)"Pacific Northwest forests" In Barbour, M.G.;Billings, W.D. (Ed.). North American terrestrial vegetation.. (pp. 103-130) Cambridge: Cambridge University Press.

Frest, T. J.,Johannes, E. J. (1995). "Interior Columbia Basin mollusk species of special concern" Seattle, WA: Deixis.

Maxwell, J. R., Edwards, C. J., et al. (1995) "A hierarchical framework of aquatic ecological units in North America (Nearctic Zone)". St. Paul, MN. North Central Forest Experiment Station, USDA Forest Service.

Sigler, J. W.,Sigler, W. F. (1994)"Fishes of the Great Basin and Colorado Plateau: Past and present forms" In Harper, K.T.;St. Clair, L.L.;Thornes, K.H.;Hess, W.M. (Ed.). Natural history of the Colorado Plateau and Great Basin. Niwot: University of Colorado Press.

Williams, J. E. (1995). "Threatened fishes of the world: Catostomus warnerensis Snyder, 1908 (Catostomidae)" Environmental Biology of Fishes 44 (4) 346.

Williams, J. E. (1995). "Threatened fishes of the world: Gila boraxobius Williams and Bond, 1980 (Cyprinidae)" Environmental Biology of Fishes 43(3) 294.

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