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Ecoregions of
North Dakota
and
South Dakota

42. Northwestern Glaciated Plains


42h. Southern River Breaks Level IV Ecoregion

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North Dakota Ecoregions

South Dakota Ecoregions

42a. Missouri Coteau

42b. Collapsed Glacial Outwash

42c. Missouri Coteau Slope

42d. Northern Missouri Coteau

42e. Southern Missouri Coteau

42f. Southern Missouri Coteau Slope

42g. Ponca Plains

42h. Southern River Breaks

42i. Glaciated Dark Brown Prairie

  The Northwestern Glaciated Plains ecoregion marks the westernmost extent of continental glaciation. The youthful morainal landscape has significant surface irregularity and high concentrations of wetlands. The rise in elevation along the eastern boundary defines the beginning of the Great Plains. Land use is transitional between the intensive dryland farming on Ecoregion 46i to the east and the predominance of cattle ranching and farming to the west on the Northwestern Great Plains (43).

GIF - Topography of river breaks
The broken topography of the river breaks (ecoregions 42h, 43c) provides valuable wildlife habitat, particularly in highly cultivated regions.

The Southern River Breaks reflect the more temperate conditions of the southern glaciated plains. Here the draws and northern aspects are heavily wooded with deciduous forest, in contrast to the River Breaks (43c) north of the Big Bend of the Missouri where the riparian woodland forms narrow stringers of juniper and green ash.

Physiography

Area (square miles): 896

Elevation/Local Relief (feet): 1250-2000/250-700

Lightly glaciated. Dissected hills and canyons with slopes of high relief bordering major rivers and associated alluvial plains.

Geology

Surficial Material and Bedrock
Cretaceous Pierre Shale.

Soil

Order (Great Groups)
Mollisols (Argiustolls), Entisols (Ustorthents)

Common Soil Series
Tuthill, Sansarc, Okaton, Manter

Temperature/Moisture Regimes
Mesic/Ustic

Climate

Precipitation - Mean annual (inches)
20-22

Frost Free - Mean annual (days)
135-160

Mean Temp. - Jan. min/max; July min/max, (°F)
7/32;60/89

Potential Natural Vegetation

Decidous woodland: cottonwood, green ash, peachleaf willow, boxelder, eastern rededar, buffaloberry, sumac. Grassland: western wheatgrass, little bluestem, sideoats grama.

Land Use and Land Cover

Grazing, wildlife habitat. Mixed grass and woodland cover.

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