Chapter 42
Ecological Subregions of the United States

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Great Plains Steppe

Five Sections have been delineated in this Province:

These Sections are located in the north-central conterminous States, including parts of Oklahoma, Kansas, Nebraska, and South and North Dakota. The area of these Sections is about 134,000 mi2 (347,100 km2).

Section 332A--Northeastern Glaciated Plains

Geomorphology. This is an area of nearly level to undulating continental glacial till and glacial lake plains, with areas of kettle holes, kames, and moraines. Some steep slopes occur adjacent to streams. Elevation ranges from 700 to 2,300 ft (214 to 704 m). This Section is within the Central Lowlands physiographic province.

Lithology and Stratigraphy. Glacial till is underlain by Cretaceous marine sedimentary rocks.

Soil Taxa. Soils include frigid Borolls with poorly drained Aquolls in depressional areas. These soils are generally deep, and textures range from sandy to clayey.

Potential Natural Vegetation. K\"uchler mapped vegetation as wheatgrass-bluestem-needlegrass. The natural prairie vegetation is dominantly western wheatgrass, needleandthread, green needlegrass, and blue grama. Little bluestem is important on sloping and thin soils. Northern reedgrass, prairie cordgrass, big bluestem, and slim sedge are important species on wet soils.

Fauna. Birds are typical prairie pothole inhabitants. This area is the most productive waterfowl breeding area in the country, especially for gadwall, mallard, pintail, blue-winged teal, and several diving ducks. Other typical pothole associated species are sandhill crane, northern harrier, piping plover, Wilson's phalarope, Franklin's gull, and marsh wren. The prairie surrounding the potholes provides habitat for a number of species: Swainson's hawk; sharp-tailed grouse; upland sandpiper; horned lark; Sprague's pipit; lark bunting; savanna, Baird's, LeConte's, and clay-colored sparrows; and chestnut-collared longspur. Rare species include least tern and bald eagle. Typical herbivores and carnivores include white-tailed deer, mule deer, and bobcat. Smaller herbivores which are common include the white-tailed jackrabbit, white-tailed prairie dog, and black-tailed prairie dog. Less common is the black-tail jackrabbit. Bison are historically associated with this Section. Typical herpetofauna are the Great Plains toad, snapping turtle, spiney softshell turtle, smooth green snake, and prairie rattlesnake.

Climate. Precipitation averages 15 to 20 in (380 to 510 mm) with more than half falling during the growing season. Winter precipitation is snow. Climate is cold continental with warm summers. Temperature averages 36 to 45 oF (2 to 7 oC). The growing season lasts 100 to 140 days.

Surface Water Characteristics. There are somewhat chaotic internal drainage patterns, with many glacial pothole lakes and ponds. Lake plains have some long, lineal drainages fed by high density dendritic drainages.

Disturbance Regimes. Fire and drought are the principal natural sources of disturbance.

Land Use. Dryland farming occurs on about 80 percent of the area.

Cultural Ecology. Reserved.

Compiled by Northern Region.

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Section 332B--Western Glaciated Plains

Geomorphology. Nearly level to undulating continental glacial till plains occur, with areas of kettle holes, kames, moraines, and glacial lake plains. Glacial lake plains and some steep slopes are adjacent to streams. Elevation ranges from 1,000 to 2,000 ft (305 to 610 m). This Section is within the Central Lowland physiographic province.

Lithology and Stratigraphy. Glacial till is underlain by Cretaceous marine sedimentary rock.

Soil Taxa. Soils include mesic and frigid Borolls and Ustolls, with poorly drained Aquolls in depressional areas. These soils are generally deep and range in texture from sandy to clayey.

Potential Natural Vegetation. K\"uchler mapped vegetation as wheatgrass-bluestem-needlegrass. The natural prairie vegetation is mainly western wheatgrass, needleandthread, green needlegrass, and blue grama. Little bluestem is important on sloping and thin soils. Northern reedgrass, prairie cordgrass, big bluestem, and slim sedge are important species on wet soils. Northern flood plain forest occurs along major drainages.

Fauna. This Section is an important migration corridor for most species of waterfowl, but especially for American coots, snow goose, mallard, and blue-winged teal. Potholes or associated wetlands provide breeding habitat for many of these species and others, such as grebe and black-crowned night-heron. Where non-grassland habitat occurs, many birds associated with eastern avifauna nearly reach their westernmost extent; these include broad-winged hawk, ruby-throated hummingbird, Philadelphia vireo, cardinal, rose-breasted grosbeak, and rusty blackbird. Other typical species include greater prairie chicken, great crested flycatcher, eastern phoebe, blue jay, brown thrasher, dickcissel, and orchard oriole. Typical herbivores and carnivores include white-tailed deer, mule deer, and bobcat. Smaller common herbivores are the white-tailed jackrabbit, white-tailed prairie dog, and black-tailed prairie dog. Less common is the black-tailed jackrabbit. Bison are historically associated with this Section. Representative herpetofauna are the Great Plains toad, snapping turtle, spiney softshell turtle, smooth green snake, and prairie rattlesnake.

Climate. Precipitation ranges from 14 to 24 in (350 to 610 mm), with more than half falling during the growing season. Winter precipitation is mostly snow. Climate is cold continental with hot, humid summers. Temperature averages 39 to 43 oF (4 to 9 oC). The growing season lasts 110 to 155 days.

Surface Water Characteristics. The Missouri river is the major drainage. Few widely spaced perennial streams occur; there are some ponds and reservoirs. Sandstones yield high quantities of mineralized artesian water, while shales yield very little water.

Disturbance Regimes. Fire and drought are the principal natural sources of disturbance.

Land Use. Dryland farming occurs on about 65 percent of the area; the rest is grazed by livestock. A small amount of the area is irrigated.

Cultural Ecology. Reserved.

Compiled by Northern Region.

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Section 332C--Nebraska Sandhills

Geomorphology. This area has rolling to steep, irregular sand dunes stabilized by vegetation, with narrow, elongated, gently rolling sloping valleys between dunes. Elevation ranges from 1,970 to 3,950 ft (600 to 1,200 m). This Section is within Fenneman and Johnson's Great Plains geomorphic physical division.

Lithology and Stratigraphy. This Section is composed of Tertiary sandstones, conglomerates, and minor shales; with Quaternary windblown dune sand and loess covering the Tertiary sandstones and conglomerates throughout much of the area.

Soil Taxa. Soils include mesic Psamments.

Potential Natural Vegetation. Mid and tall grass plant communities are present including Nebraska sandhills prairie (bluestem, sandreed). K\"uchler classified vegetation as sandhills prairie, wheatgrass-bluestem-needlegrass, and, along major drainages, northern flood plain forest.

Fauna. Bison and wolves are historically associated with this section. Current large mammals include white-tailed deer, and mule deer and pronghorn antelope, for which this is the eastern range. Smaller mammals typical of the area are jackrabbit, cottontail, prairie dog, bobcat, and red fox. Typical year-round avifauna include bobwhite, greater prairie chicken, and mallard. Kestrel, eastern bluebird, swallow, and belted kingfisher are summer nesters. The northern extent of the sharp-shinned hawk's winter range lies in the Section, and the goldeneye duck is a winter resident. Typical herpetofauna are the snapping turtle, painted turtle, Great Plains toad, plains hognose snake, and bull snake. Catfish are common in rivers and ponds.

Climate. Precipitation ranges from 17 to 23 in (430 to 580 mm). Temperature averages 48 to 52 oF (9 to 11 oC). The growing season lasts 140 to 150 days.

Surface Water Characteristics. There are many small lakes and ponds and a few streams. Ground water is abundant and of good quality. The Niobrara, North and Middle Loup, Snake, Dismal, Elkhorn, Calamus, and Cedar Rivers flow through here.

Disturbance Regimes. Fire, insect and disease are predominant natural disturbances.

Land Use. Nearly all of this area is in large ranches, most of which are grazed. Use of sprinkler irrigation has increased over recent years.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.

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Section 332D--North-Central Great Plains

Geomorphology. There are nearly level to gently rolling till plains with potholes and well defined dendritic drainage system. Moderate to steep slopes are adjacent to major valleys. River and creek valleys have smooth floors and steeps walls. Higher parts of tablelands are moderately sloping, but steeper areas occur on ridges and drainage ways. Drainages are well defined except in some undulating areas where eolian materials cover the bedrock. Elevation ranges from 1,310 to 2,950 ft (400 to 900 m). This Section is within Fenneman and Johnson's Great Plains geomorphic physical division.

Lithology and Stratigraphy. Most of the Section is Cretaceous marine shale, with local Tertiary sandstones and claystones in the extreme south.

Soil Taxa. Mesic temperature and ustic moisture regimes occur. Soils include Mollisols, including Agriborolls and Haplustolls.

Potential Natural Vegetation. K\"uchler mapped potential vegetation as wheatgrass-needlegrass prairie and wheatgrass-bluestem-needlegrass prairie and wheatgrass-bluestem-needlegrass prairie with northern flood plain forests along the Missouri River lowlands. Other communities consist of mixed and natural prairie.

Fauna. Bison are historically associated with this Section, and black-footed ferrets are former inhabitants. White-tailed deer and a smaller population of mule deer are current herbivores. Small herbivores include the jackrabbit and prairie dog. Bobcat, red fox, and swift fox are present. Prairie potholes are important habitat for many species of migrating waterfowl. Horned lark, bobwhite, and greater prairie chicken are year-round residents. Summer residents include burrowing owl and belted kingfisher in riparian zones. Dark-eyed junco and pine siskin are winter residents. Typical herpetofauna include the Great Plains toad, snapping turtle, painted turtle, and prairie rattlesnake. Black crappie and catfish are common fish species.

Climate. Precipitation averages 15 to 24 in (370 to 600 mm). Temperature averages 45 to 50 oF (7 to 10 oC). The growing season lasts 130 to 160 days.

Surface Water Characteristics. The Missouri, Niobrara, and White Rivers flow through here. There is a limited supply of ground water available. Shallow water developments exist, such as dug ponds and small reservoirs. Some deep artesian wells exist. Reservoirs occur on the Missouri river.

Disturbance Regimes. Fire, insects, and disease are the primary natural disturbances.

Land Use. Most of the area is in farms or ranches, with limited urban expansion. About 50 percent of the area is in dry crops. Grazing is common, especially on the Dakota-Nebraska Tableland. Irrigation occurs along the Missouri River.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.

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Section 332E--South-Central Great Plains

Geomorphology. Gently sloping loess-mantled narrow ridgetops are separated by steep slopes bordering drainage ways. Some stream valleys with nearly level flood plains and large stream terraces exist. Dissected plains with broad rolling ridgetops and moderately steep valley sides occur. Valleys are usually narrow with broad flood plains and terraces, and hilly dissected plains. There are rivers with wide flood plains and terraces, and small streams with narrow bottomlands. Rolling plains have a deep mantle of windblown sand and sandy outwash. Elevation ranges from 1,310 to 2,950 ft (400 to 900 m). This Section is within Fenneman and Johnson's Great Plains geomorphic physical division.

Lithology and Stratigraphy. Most of Section is Cretaceous marine shales, with some sandstones in the extreme northwest. Quaternary windblown dune sands and loess often cover the Cretaceous shales.

Soil Taxa. There are mesic and therimc temperature and ustic moisture regimes. Soils include Mollisols and Alfisols.

Potential Natural Vegetation. Predominant vegetation is grass and prairie communities. K\"uchler mapped vegetation as bluestem-grama prairie, sandsage-bluestem prairie, northern flood plain forests, and buffalograss.

Fauna. Bison, wolves, and black-footed ferrets are historically associated with this Section. Present large mammals include white-tailed deer, mule deer, and a small population of pronghorn antelope. Typical small mammals include bobcat, red fox, jackrabbit, cottontail, and prairie dog. Typical year-round avifauna include the introduced ring-necked pheasant, horned lark, bobwhite, Cooper's hawk, and prairie falcon. Summer nesters include Swainson's hawk, blue-winged teal, and ruddy duck. The goshawk may be a rare winter resident. The goldeneye and common merganser are other winter residents. Herpetofauna include snapping turtle, Great Plains toad, western hognose snake, and the western garter snake. Catfish species are typical in area waters.

Climate. Precipitation ranges from 20 to 35 in. (500 to 900 mm). Temperature averages 50 to 61 oF (10 to 16 oC). The growing season lasts 150 to 230 days.

Surface Water Characteristics. Large rivers, streams, ponds, reservoirs, and wells exist in this Section. Ground water is abundant in areas associated with sand and gravel deposits; however, it is scarce and may be mineralized in areas where shale, sandstone, clay, and limestone are near the surface. Many rivers flow through this Section, including the Platte, Loup, Republican, Cimarron, Arkansas, Solomon, and Saline. Large reservoirs include Johnson, Harlan, Wilson, Waconda, and Cheney.

Disturbance Regimes. Fire, insects, and disease are primary natural disturbances.

Land Use. Most of the Section is in farms and ranches. About 60 percent of the area is in crop land. About 35 percent of the area is grazed. Irrigation occurs along rivers in most of the area accounting for approximately five percent of the total area; however, in the central area, where corn is the major cash crop, it is irrigated extensively.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.

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