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Ecoregions of
North Dakota
and
South Dakota

43. Northwestern Great Plains


43i. Keya Paha Tablelands Level IV Ecoregion

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North Dakota Ecoregions

South Dakota Ecoregions

43a. Missouri Plateau

43b. Little Missouri Badlands

43c. River Breaks

43d. Forested Buttes

43e. Sagebrush Steppe

43f. Subhumid Pierre Shale Plains

43g. Semiarid Pierre Shale Plains

43h. White River Badlands

43i. Keya Paha Tablelands

43j. Moreau Prairie

43k. Dense Clay Prairie

  The Northwestern Great Plains ecoregion encompasses the Missouri Plateau section of the Great Plains. It is a semiarid rolling plain of shale, siltstone, and sandstone punctuated by occasional buttes and badlands. Native grasslands persist in areas of steep or broken topography, but they have been largely replaced by spring wheat and alfalfa over most of the ecoregion. Agriculture is limited by erratic precipitation patterns and limited opportunities for irrigation.
The Keya Paha Tablelands form a perimeter of sandy, level to rolling plains that surround the steeper dune topography of the Nebraska Sand Hills (44a). Ponderosa pines grow in the drainages in the hilly land east of the Pine Ridge escarpment. Millet and corn grow on the level land, but the sandy soil limits nonirrigated agriculture.

Physiography

Area (square miles): 3451

Elevation/Local Relief (feet): 2250-3600/20-800

Unglaciated. Level to rolling, sandy plains. Dissected near streams.

Geology

Surficial Material and Bedrock
Eolian and alluvial sand and silt over Miocene soft sandstone (Ogallala Formation).

Soil

Order (Great Groups)
Mollisols (Argiustolls, Haplustolls), Entisols (Torriorthents)

Common Soil Series
Anselmo, Kadoka, Keith, Manter, Rosebud, Epping, Keota, Ronson, Vetal.

Temperature/Moisture Regimes
Mesic/Ustic

Climate

Precipitation - Mean annual (inches)
16-20

Frost Free - Mean annual (days)
120-140

Mean Temp. - Jan. min/max; July min/max, (°F)
9/34;59/89

Potential Natural Vegetation

Blue grama, sideoats grama, western wheatgrass, little bluestem, and needleandthread.

Land Use and Land Cover

Cattle ranching predominates north with some dryland farming for alfalfa and winter wheat. Corn and sugar beets in irrigated areas south. Mixed prairie range with cropland.

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