The Northern Glaciated Plains ecoregion is characterized by a flat to gently rolling landscape composed of glacial drift. The subhumid conditions foster a grassland transitional between the tall and shortgrass prairie. High concentrations of temporary and seasonal wetlands create favorable conditions for duck nesting and migration. Though the till soil is very fertile, agricultural success is subject to annual climatic fluctuations.

The Big Sioux Basin is a trough penetrating the core of the Prairie Coteau (46k). Its topography was affected by pre-Wisconsinan glaciation; later advances of the Wisconsin glacier diverged around the basin. In contrast to the neighboring Prairie Coteau (46k), the basin has a well-developed drainage network. There is more tilled land in the Big Sioux basin due to the relative paucity of wetlands and the gentler topography.

Physiography

Area (square miles): 1539
Elevation/Local Relief (feet): 1625-1990/20-200
Only lightly glaciated. Erosional, rather than depositional landscape. Rolling, with incised stream drainage network, few wetlands.

Geology

Surficial Material and Bedrock
Glacial till over Cretaceous Pierre Shale

Soil

Order (Great Groups)
Mollisols (Haploborolls)
Common Soil Series
Brookings, Kranzburg, Vienna, Lismore
Temperature/Moisture Regimes
Frigid/Udic

Climate

Precipitation - Mean annual (inches)
20-22
Frost Free - Mean annual (days)
110-140
Mean Temp. - Jan. min/max; July min/max, (°F)
2/22;60/85

Potential Natural Vegetation

Tallgrass prairie: big and little bluestem, switchgrass, and indiangrass, sideoats grama, lead plant. Riparian vegetation: willows and cordgrass north; more hardwoods south.

Land Use and Land Cover

Extensively tilled for small grains, corn, sunflowers, and soybeans.

Ecoregions of North Dakota and South Dakota

Ecoregions of
North Dakota
and
South Dakota