Section 331F Northwestern Great Plains
Geomorphology. This area includes gently sloping to rolling, moderately dissected shale plains. There are some steep, flat-topped buttes, particularly in eastern Wyoming. Badlands with eroded escarpments are in North Dakota and western South Dakota. Elevation ranges from 1,500 to 3,900 ft (458 to 1,200 m). This Section occurs on the Missouri Plateau and High Plains within the Great Plains physiographic province.
Lithology and Stratigraphy. This Section has soft Cretaceous and Lower Tertiary non-marine sedimentary rocks.
Soil Taxa. Soils include mesic and frigid Borolls and Ustolls, particularly in the northern, southern, and eastern parts of the Section. These soils are generally moderately deep to deep and have loamy to clayey textures. Argids, Orthents, and Orthids also occur, mostly in the central and western parts of the Section and on the badlands. These soils range from shallow to deep and generally have clayey textures.
Potential Natural Vegetation. Kuchler mapped vegetation as wheatgrass-needlegrass. Most of the Section has natural prairie vegetation, which includes western wheatgrass, green needlegrass, blue grama, needleandthread, and buffalograss. Bluebunch wheatgrass, little bluestem, and sideoats grama occur on shallow soils. Common shrubs in draws and along streams include buffaloberry, chokecherry, snowberry, and sagebrush. Ponderosa pine, juniper, and some aspen occur in North Dakota and on the Pine Ridge in South Dakota.
Fauna. Birds are dry grassland and badland species, and riparian associates. Typical species are ferruginous hawk, golden eagle, sharp-tailed grouse and sage grouse, gray partridge, mourning dove, black-billed magpie, horned lark, western meadowlark, lark bunting, grasshopper sparrow, and chestnut-collared longspur. Riparian or wetland associated species include dabbling duck, eastern kingbird, blue jay, brown thrasher, and yellow warbler. Species near the edge of their range include chimney swift; eastern, western and mountain bluebirds; dickcissel; field sparrow; and orchard oriole. Typical herbivores and carnivores include white-tailed deer, mule deer, pronghorn, and bobcat. 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 bighorn sheep and the black-tailed jackrabbit. Rare species includes the black-footed ferret. Bison are historically associated with this Section. Herpetofauna typical of this Section are the snapping turtle, spiney softshell turtle, smooth green snake, and prairie rattlesnake.
Climate. Precipitation ranges from 10 to 20 in (250 to 510 mm), with more than half falling during the growing season. Winters are extremely cold with desiccating winds. Precipitation is snow. Climate is cold continental. Temperature averages 37 to 48 F (3 to 9 C). The growing season lasts 110 to 160 days.
Surface Water Characteristics. There are long, structurally controlled second and third order streams with low gradient, which are fed by high density, dendritic first order tributaries. Alternating hard and soft layers at low angles produce a complex pattern of resistant layers, temporary base levels, and headward and sideward erosion by undercutting. Ground water is scarce over most of the area but does occur locally in sand and gravel deposits. Major rivers include the Missouri, Cheyenne, Little Missouri, and Niobrara.
Disturbance Regimes. Fire and drought are the principal natural sources of disturbance.
Land Use. Dryland farming and livestock grazing occur on about 85 percent of the area. Some commercial timber harvests also occur.
