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Ecoregions of
North Dakota
and
South Dakota

43. Northwestern Great Plains


43k. Dense Clay Prairie 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 Dense Clay Prairie differs from the surrounding ecoregions in its lack of vegetative cover. The grassland in this ecoregion is missing its short- and mid-level layers. Only the tall grasses show thinly against the dark-colored clay. Riparian woodland is absent from draws and stream corridors. This fragile landscape must be managed carefully to avoid erosion and blowing soil. Sheep farming is the major land use.

Physiography

Area (square miles): 1378

Elevation/Local Relief (feet): 2700-3500/150-450

Unglaciated. Rolling prairie. intermittent streams in shallow valleys.

Geology

Surficial Material and Bedrock
Cretaceous Pierre shale.

Soil

Order (Great Groups)
Vertisols (Haplusterts, Torrerts), Aridisols (Natrargids), Entisols (Torriorthents)

Common Soil Series
Kyle, Pierre, Winler, Swanboy, Hisle, Lismas

Temperature/Moisture Regimes
Mesic/Ustic, Aridic

Climate

Precipitation - Mean annual (inches)
13-15

Frost Free - Mean annual (days)
120-130

Mean Temp. - Jan. min/max; July min/max, (°F)
6/30;58/87

Potential Natural Vegetation

Western wheatgrass with no shortgrass understory.

Land Use and Land Cover

Sheep and cattle ranching. Fragile grassland cover.

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