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Ecoregions of
North Dakota
and
South Dakota

25. Western High Plains


25a. Pine Ridge Escarpment Level IV Ecoregion

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25a. Pine Ridge Escarpment

  The Western High Plains ecoregion is a landscape of rolling plains and tablelands formed by the erosion of the Rocky Mountains. Moisture is a limiting factor in the rainshadow of the Rocky Mountains; as a result, the plains vegetation is dominated by drought resistant shortgrass prairie. Farming in this region, once dependent upon rainfall, has been supplemented by irrigation water from the Ogallala Aquifer.

JPG - Hillside with trees

The Pine Ridge Escarpment forms the boundary between the Missouri Plateau to the north and the High Plains to the south. Ponderosa pine clothe the northern face and the ridgecrest outcrops of sandstone. Cattle graze the rolling grasslands of the Pine Ridge Indian Reservation. A mixed-grass prairie vegetation, rather than shortgrass prairie, dominates this northern extremity of the Western High Plains (25).

Physiography

Area (square miles): 965

Elevation/Local Relief (feet): 3000-3700/50-700

Unglaciated. Alternating ridges and valleys with entrenched channels. Elevations increasing from northeast to southwest. Rock outcrops.

Geology

Surficial Material and Bedrock
Miocene sandstone (Arikaree Formation)

Soil

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

Common Soil Series
Ogallala, Canyon, Kadoka, Epping, Rock outcrops

Temperature/Moisture Regimes
Mesic/Ustic

Climate

Precipitation - Mean annual (inches)
16-17

Frost Free - Mean annual (days)
120-140

Mean Temp. - Jan. min/max; July min/max, (°F)
9/36;58/91

Potential Natural Vegetation

Poderosa pine savannah with eastern redcedar, western snowberry, skunkbush sumac, chokecherry, and rose. Grassland: little bluestem, western wheatgrass, green needlegrass, prairie sandreed.

Land Use and Land Cover

Cattle grazing, minor hay and feed crops, and some timber cutting. Pine savannah.

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