Section 331D Northwestern Glaciated Plains
Geomorphology. This Section includes level to gently rolling continental glacial till plains and rolling hills on the Missouri Plateau. Steep slopes border some of the larger rivers. Elevation ranges from 2,500 to 5,000 ft (763 to 1,525 m). This Section is within the Great Plains physiographic province.
Lithology and Stratigraphy. Glacial till is underlain by soft Cretaceous marine shale.
Soil Taxa. Soils include frigid Borolls, Ustochrepts, Natriborolls, and Orthents with some Fluvents along the rivers. These soils are generally deep and range in texture from loamy to clayey.
Potential Natural Vegetation. Kuchler mapped vegetation as grama-needlegrass-wheatgrass. Common species include blue grama, bluebunch wheatgrass, green needlegrass, needleandthread, western wheatgrass, and basin wildrye.
Fauna. Birds are typically grassland associated species or those associated with prairie potholes. These include the ferruginous hawk, Swainson's hawk, golden eagle, sharp-tailed grouse and sage grouse, mountain plover, clay-colored sparrow, and dabbling ducks. Riparian areas also provide for some woodland species at the edge of their ranges such as eastern screech-owl, red-headed woodpecker, and ovenbird. Other species which nearly reach the edge of their ranges in this Section are Sprague's pipit and Baird's sparrow. Typical herbivores and carnivores include white-tailed deer, mule deer, pronghorn, bobcat, and cougar. Smaller common herbivores include the white-tailed jackrabbit, white-tailed prairie dog, and black-tailed prairie dog. Less common species associated with this Section includes black-tailed jackrabbit, swift fox, dwarf shrew, and Canadian toad. The black-footed ferret and bison are species which historically occurred here. Herpetofauna typical of this Section are the snapping turtle, spiney softshell turtle, smooth green snake, and the prairie rattlesnake.
Climate. Precipitation averages 10 to 15 in (250 to 380 mm), with maximum occurring in spring and early summer. Winters are extremely, cold with desiccating winds and snow. Climate is cold continental, with dry winters and warm summers. Temperature averages 37 to 45 F (3 to 7 C). The growing season lasts 100 to 130 days.
Surface Water Characteristics. There are high density dendritic drainage patterns on areas of exposed marine shales. Low to medium density drainage patterns occur on the better drained glacial till. The higher order streams show subtle structural and glacial influence. Major rivers include the Milk and the Poplar.
Disturbance Regimes. Fire and drought are the principal sources of natural disturbance.
Land Use. Most of the area is in crop land or is grazed by livestock.
