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Ecoregions of
North Dakota
and
South Dakota

43. Northwestern Great Plains


43f. Subhumid Pierre Shale Plains 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.

GIF - Soft shales
Overgrazing or tilling the soft shales of ecoregions 43f and 43g risks wind and water erosion

A continuous vegetative cover is essential to keep the Subhumid Pierre Shale Plains intact. Tilling the rolling hillsides risks wind and water erosion. Stream channels are deeply incised in its soft, black shale soils and slumping is common along exposed banks.

Physiography

Area (square miles): 7544

Elevation/Local Relief (feet): 1700-2800/50-500

Unglaciated. Undulating plain. Steep-sided, incised stream channels.

Geology

Surficial Material and Bedrock
Cretaceous Pierre shale.

Soil

Order (Great Groups)
Mollisols (Argiustolls, Haplustolls), Inceptisols (Ustochrepts), Entisols (Ustorthents, Torriorthents), Vertisols (Hapllusterts)

Common Soil Series
Millboro, Lakoma, Opal, Promise, Sansarc, Midway, Ottumwa

Temperature/Moisture Regimes
Mesic/Ustic

Climate

Precipitation - Mean annual (inches)
15-17

Frost Free - Mean annual (days)
110-135

Mean Temp. - Jan. min/max; July min/max, (°F)
4/29;60/91

Potential Natural Vegetation

Wheatgrass, grama grass, needlegrass, porcupine grass, needleandthread.

Land Use and Land Cover

Cattle grazing, dryland farming. Winter wheat, alfalfa and sorghum.

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