Naturally Occurring Vegetative Cover Types of South Dakota

Presented here are brief descriptions of 35 naturally occurring vegetative cover types that were used to characterize prevailing vegetation of Ecoregion "sections" of the conterminous United States. Cover types may be visualized as the general, natural vegetation viewed from an aerial perspective. These cover types are used for descriptive purposes in the section narratives and should not be confused with potential natural vegetation (PNV), which was used in the process of identification and delineation of larger ecological units. Some cover types are similar to PNV, particularly in forested regions. Other cover types, such as the prairie type, are present only in small areas that have been changed to agricultural type. For example, cover types may result from exclusion of some types of natural disturbance, such as fire, and include planned disturbances, such as harvesting. THE PONDEROSA PINE COVER TYPE   View/ Download a printable PDF version  Physiography Because ponderosa pine has a rather wide range of adaptability and can dominate some of the less mesic true forest sites, it occupies low mountains and foothills in many places; yet in mixtures with other species, it is found at moderate elevations. The extensive distribution of ponderosa pine and associates includes parts of 14 western states from Nebraska to the Pacific coast and from Arizona to Canada. It is the largest western forest type in the United States. Local topography can be gentle, as on plateau tops and low mountains, or it can be steep, as on canyon walls and faces. Semiarid, low mountain sites are common, but it is difficult to characterize the physiography of the cover type because it varies greatly. Climate The length of the frost-free season at any location in the cover type depends largely upon the latitude and elevation. In general, in much of the northern area the frost-free period is 120 days, whereas in many foothill areas and in parts of the Sierra and the Gila Mountains of the Southwest, it can be 240 days. Annual precipitation is about 15-20 inches in the more pure pine areas, but where there are combinations of pine and other conifers at moderate elevations, the precipitation can total 30 inches. In the far western sector, only 25 percent of this moisture falls in the warmest months. In the northern Rocky Mountains, 40-50 percent of the precipitation occurs in the warmest months. In the middle to southern Rockies, 66-75 percent occurs in the warmest months. In the southern areas and those at low elevations, precipitation during the frost-free season is only 20 percent of the evaporation potential. In northern areas precipitation during the growing season may be as high as 40 percent of the evaporation potential.  Vegetation  By definition, ponderosa pine forest is 50 percent or more of one of these pines: ponderosa pine, Jeffrey pine, sugar pine, limber pine, Arizona ponderosa pine, Apache pine, or Chihuahua pine. The exceptions are those situations where western white pine or sugar pine comprises 20 percent or more of the stand; then these species control the name of the forest. The impact of logging and ecological dynamics can cause some problems in maintaining good delineation of the ponderosa pine cover type. This cover type is idealized as open and parklike with an excellent ground cover of grasses, sedges, and forbs or with an understory of shrubs of low to medium height. The shrubs, however, may vary from antelope bitterbrush in Oregon to bearmat in the Sierra Nevada in California. In perhaps 60 percent of the area, the idealized open character of the ponderosa pine cover type has changed to that of a dense and growth-retarded stand, particularly in the Pacific Northwest. Fauna In the ponderosa pine cover type, the major mammalian influents are the Rocky Mountain elk, mule deer, mountain lion, and coyote. Animals of less importance include the bushy-tailed wood rat, white-footed mouse, bobcat, rock squirrel, cottontail, porcupine, mantled ground squirrel, Kaibab squirrel, and chipmunks. The Kaibab squirrel is rare. It is endemic to this cover type on Arizona's Kaibab Plateau.  The most abundant and important resident birds in the ponderosa pine cover type include the pygmy nuthatch, long-crested jay, sharp-shinned hawk, Rocky Mountain nuthatch, mountain chickadee, Cassin's purple finch, red-shafted flicker, red-backed junco, western goshawk, and western red-tailed hawk. Birds that are common during the summer include the chestnut-backed bluebird, Audubon's warbler, Natalie's sapsucker, western chipping sparrow, horned owl, and band-tailed pigeon. Soils The soils occupied by the ponderosa pine cover type vary tremendously. Along the western edge of the Columbia Plateau and the east slope of the Cascade Mountains, they are Mollisols, Inceptisols, Entisols, and Aridisols. In northern and eastern California, ponderosa pine stands are associated with Ultisols. At the northern edge of the Columbia Plateau (Okanogan Highlands) and in much of the northern Rocky Mountains, pine and the related forest types occur on Inceptisols; the soils of the rest of these areas are largely Alfisols and Entisols. In the Blue and Wallowa Mountains of eastern Oregon, pine stands occupy Mollisols. In the middle and southern Rocky Mountains, pines and associates are on Mollisols, Aridisols, Entisols, and Alfisols. Pine stands in the Gila Mountains are largely on Mollisols. The small stands of pine in the Great Basin are on Aridisols. Land Use Ponderosa pine lands continue to be producers of softwood that is highly desired for either millwork or framing. The forage supply within the cover type has been highly prized for summer range, because the land is usually high enough to get good precipitation and the forest soils are deep enough to store sufficient water for growing timber and good ground cover. These precipitation and soil characteristics make the cover type productive of forage during the hot months when range forage at lower elevations has dried. Data Source: United States Department of Agriculture, Forest Service THE FIR-SPRUCE COVER TYPE   View/ Download a printable PDF version  Physiography The fir-spruce cover type lies within the Sierra-Cascade and the northern, middle, and southern Rocky Mountains provinces. It is normally the highest forest zone in the mountain ranges but varies from as low as 1,500 feet in the Northwest to as high as 12,000 feet in the southern Rocky Mountains. Much of the topography is rough and broken. Climate  Annual precipitation ranges from somewhat fewer than 22 inches in the Rocky Mountains to 50-75 inches in the Sierras. In the Rockies, 50-65 percent of the precipitation falls in the warmest months, while in the Sierra-Cascade Mountains province only 25-40 percent falls in the warmest months. Precipitation in the period December to March is 50-60 percent of the annual total in the Sierra-Cascade Mountains and 15-25 percent in the Rocky Mountains. During the frost-free season, precipitation is 20- 40 percent of the evaporation potential. Vegetation The fir-spruce cover type is characterized by open to dense forests of low to tall needle-leaved evergreen trees and patches of shrubby under growth and scattered herbs. Fifty percent or more of the stand is silver fir, subalpine fir, red fir, white fir, mountain hemlock, Engelmann spruce, or blue spruce, singly or in combination, except where western white pine comprises 20 percent or more of the stand (in which case the cover type would be classified as western white pine). Because of the dense overstory and limited understory, heavily stocked stands are usually not considered a forage resource for domestic livestock unless timber is harvested by patch clearcuts. Fauna Seasonally, the fir-spruce cover type and, in particular, the interspersed openings and stream bottoms with broad-leaved woody species such as aspen and willows, are used by moose, elk, mule deer, and white-tailed deer. Mountain caribou originally wintered in Idaho, Washington, and Montana; a few still do. The wolverine, lynx, black bear, mountain lion, coyote, and wolf occur in the cover type. The grizzly bear is present, though in a fraction of its original numbers and is classified as a rare species. Grizzlies are about the only predator of elk and possibly are a useful natural control over excessively large elk herds. Animals Several of the species that have been mentioned use the fir-spruce cover type only seasonally, primarily as cover or in following migratory routes. This is the case with the mountain sheep and the mountain goat, which occur more commonly in steep rocky areas. Among the birds in the cover type are several of the blue grouse and spruce grouse groups, ruffed grouse, and various chickadees, nuthatches, bluebirds, robins, and jays. Among the more common rodents and lagomorphs are the porcupine, beaver, snowshoe rabbit, squirrels, flying squirrels, pocket gophers, chipmunks, and various species of mice.  Soils  The soils of this cover type are extremely varied. In the Northwest, Inceptisols (Cryandepts and Cryumbrepts) predominate. Ultisols occur in the Sierra Nevada Range. Alfisols (Boralfs) are common in the Rocky Mountains, and there are also significant areas of Entisols. Areas of deep overburdens of absorptive Vitrandepts are very productive sites in eastern Oregon and the northern Rockies. Land Use Heavy forests cover much of the cover type, and they are used as wildlife habitats and watersheds and for recreation and lumbering. There is virtually no cropland. Much of the area is owned by the Federal Government. Data Source: United States Department of Agriculture, Forest Service THE WESTERN HARDWOODS COVER TYPE   View/ Download a printable PDF version  Physiography The western hardwoods cover type occurs in northern California and southern Oregon on tablelands where 50-80 percent of the area is gently sloping and the relief is only 300-500 feet and on low mountains where slopes are mostly steep and the local relief is 1,000-3,000 feet. It also occurs in the Rocky Mountains, and this portion of the cover type (mostly aspen areas) varies considerably. Climate The west coast portion of this cover type has rainy winters and dry summers. Annual precipitation ranges, on the average, from 15 inches in California to 48 inches in Oregon and occurs mostly as rain between the months of November and May. Normal annual pan evaporation ranges from about 40 inches in Oregon to nearly 100 inches in southern California. Evaporation during the frost-free season ranges from about two to five times the potential evaporation. The climate of the widely scattered Rocky Mountain portions corresponds to that described for adjacent or surrounding cover types.  Vegetation This cover type is characterized by forests in which 50 percent or more of the stand is hardwood species, except where western white pine, sugar pine, or redwood comprises 20 percent or more of the stand (in such cases the cover type is classified as western white pine or redwood). The vegetation is a forest of low- to medium-tall, broad-leaved deciduous or evergreen trees, sometimes with an admixture of low- to medium-tall needle-leaved evergreens, often with an understory of grass and shrubs. In the California and Oregon portions of this cover type, dominant species include Oregon white oak, Coulter pine, Digger pine, coast live oak, canyon live oak, blue oak, valley oak, and interior live oak. In California, this cover type lies mainly between the annual grasslands and the chaparral and mixed conifer zones. The widely scattered Rocky Mountain and Plains States "hardwood" portion of the cover type consists primarily of quaking aspen stands with an understory of grasses, forbs, and shrubs. In many places where the aspen stands are inclusions within areas of sagebrush or conifers, they are important sources of food and cover for wildlife. Cottonwood becomes dominant on plains, more or less replacing aspen. Fauna In California, several subspecies of mule deer are numerous in various parts of this cover type. The now-extinct California grizzly was once numerous. An occasional black bear comes down from forests at higher elevations. Mountain lions are no longer numerous; the largest numerous predatory animals are the coyote and the bobcat.  Avian predators include golden eagles and red-tailed and other hawks. Two endangered species, the California condor and the San Joaquin kit fox, occur. California quail are often abundant at lower elevations, and mountain quail winter at the higher elevations. The striped skunk is widespread. Among the more common small mammals are the Beechy ground squirrel, kangaroo rat, pocket gopher, and a number of types of mice. Also occurring in this part of this cover type are additional species found in the annual grasslands cover type. The fauna of the Oregon oakwoods portion of the cover type is somewhat similar to that in the California portion, but species representative of the southernpart of the California oakwoods may not be present and more northern species, such as the ruffed grouse, are present. Deer are common; elk were numerous in the past. The western gray squirrel frequents stands of Garry oak.  The fauna of the aspen portion of the cover type throughout the Rocky Mountain area is essentially that of the adjacent or surrounding cover types, but the aspen stands serve as important areas of food and shelter for many species of wildlife. Where hardwood stands occur on river bottoms in the plains, they are a home for many arboreal and forest-edge species that are not present in the surrounding open country.  Soils  In Oregon, the soils of this cover type are deep and have well-developed illuvial horizons (Argixerolls). Drainage is generally good. Farther south, in California, the surface horizons are somewhat lighter and lower in content of organic matter, but the illuvial horizon of accumulated clay is again present (Xeralfs). Land Use Livestock grazing in the cover type is limited to the more open portions of stands adjacent to grasslands. Wildlife find cover in the several variations of the cover type, and the aspen portions provide browse for big game. Data Source: United States Department of Agriculture, Forest Service THE SAGEBRUSH COVER TYPE   View/ Download a printable PDF version  Physiography The sagebrush cover type is prominent principally on the Columbia Plateaus in the northwestern states; in the central portion of the Great Basin in Utah, Nevada, and southern Idaho; in the Wyoming Basin; and on the Colorado Plateaus and some of the lower reaches of adjacent mountains. This broad cover type occupies vast plains and plateaus derived from lava flows, ancient lake beds, and broad basins of alluvium. The more individual plateau sections are usually delineated in terrace and tablelike fashion and range from rolling lava plains to maturely fringed and dissected mesas. Elevations range roughly from 600-10,000 feet. Climate The length of the frost-free season normally is 120 days but is reduced to only 80 days at certain mountain sites. Annual precipitation is 5-12 inches (in some places almost 20 inches), and 40-50 percent of it comes in the period December to March. Only 25-40percent occurs in the warmer half of the year. Precipitation is only 20 percent of the evaporation potential during the frost-free season.  Vegetation The sagebrush cover type is characterized by shrubs, principally of the genus Artemisia, which are usually 1-7 feet high. In some situations, other shrubs are part of the vegetation. In other places, grasses such as those of the genera Agropyron, Festuca, Poa,and Bromus,as well as broad-leaved herbs, are found in the understory. Fauna Pronghorn, or antelope, use parts of this cover type as rangeland throughout the year, whereas mule deer prefer to use sagebrush rangeland only during the winter. The Utah prairie dog is an endangered species of this cover type. Other wild mammals that are principal inhabitants of this cover type are the Great Basin coyote, black-tailed jackrabbit, pygmy cottontail, Ord's kangaroo rat, and Great Basin kangaroo rat. Bird populations are low during the breeding season, averaging only about 25 pairs per 100 acres. The major influent birds include the marsh hawk, red-tailed hawk, Swainson's hawk, golden eagle, bald eagle, Cooper's hawk, prairie falcon, burrowing owl, and long-eared owl. The sage grouse and chukar are important game birds. More than 50 additional species of birds nest within the cover type.  Soils In the Columbia Plateaus province, the sagebrush cover type occupies Mollisols having black, friable, organic surface horizons and a high content of bases. Inceptisols (Andepts) of ashy nature are conspicuous in parts of the Columbia Plateaus. In the Great Basin and part of the Wyoming Basin, the soils of the sagebrush cover type are Aridisols which have pedogenic horizons, are low in content of organic matter, have a clay horizon in some places, and have accumulations of various salts in some places. In part of the Colorado Plateaus province, as well as part of the Wyoming Basin, they are Entisols, which have no pedogenic horizons. The remaining soils of the sagebrush cover type in the Colorado Plateaus province are Aridisols and Mollisols. Land Use Most of the land within the sagebrush cover type is used for sheep and cattle grazing, principally in the spring and fall. Where sufficient water is available, irrigation ranching and farming are practiced. The principal crops are hay, grain, potatoes, and beets. Data Source: United States Department of Agriculture, Forest Service THE PLAINS GRASSLANDS COVER TYPE   View/ Download a printable PDF version  Physiography The plains grasslands cover type, also known as the Great Plains, occurs on a broad belt of high land that slopes gradually eastward and down from an altitude of 5,500 feet near the eastern foothills of the Rocky Mountains to an altitude of 1,500 feet in the central states, where it gives way to the prairie cover type.  The most striking feature of the cover type is the phenomenal flatness of the inter stream areas, which make up a great expansive fluviatile plain or alluvial slope. The eastern margin has been most exposed to erosion, being near the trunk line of drainage and in a climate of greater rainfall than the western edge. The plains grasslands cover type of 280 million acres is larger than any other vegetation region in the United States. Climate Temperatures vary considerably, the frost-free season ranging from less than 100 days in the north to more than 200 days in Texas. The cover type is characterized by periodic droughts. Average annual precipitation ranges from 10 inches in the north to more than 25 inches in the south, 68-80 percent of the precipitation falling in the warmest months. Normal annual pan evaporation is roughly four times the precipitation. Precipitation ranges from about one-third to one-half of potential evaporation. Vegetation Short, warm-season grasses predominate in this cover type, and there is a minor interspersion of forbs and shrubs. Vast stretches are dominated almost exclusively by blue grama, buffalo grass being a companion in many areas. The eastern part of the cover type, however, is dominated by grasses of medium stature, such as western wheatgrass and needlegrass. The occasional shrubs include juniper, silver sagebrush, silver buffalo berry, and skunk bush sumac in the northern reaches and rabbit brush and mesquite in the southern part. Forbs are generally quite common, but many are ephemerals. Fauna Huge herds of American bison once migrated with the seasons across the central plains. Currently, the pronghorn, or antelope, is probably the most abundant large mammal, but mule deer and white-tailed deer are often abundant where brush cover is available, as along stream courses. The white-tailed jackrabbit occupies the northern part of the cover type, and the black-tailed jackrabbit can be found in the area south of Nebraska. The desert cottontail is widespread. The lagomorphs, the prairie dogs, and a variety of small rodents are preyed upon by the coyote and a number of other mammalian and avian predators, one of which, the black-footed ferret, is classed as an endangered species. The wolf once existed on the plains in great numbers, feeding to a considerable extent on bison. The lesser prairie chicken, formerly abundant, is now classed as a rare species. Sage grouse, greater prairie chickens, and sharp-tailed grouse are present in the area. Among the many smaller birds are the horned lark, lark bunting, and western meadowlark. The endangered golden-cheeked warbler is in the southeastern portion of the cover type in places where the Ashe juniper is present. Stock pond construction has created an important "duck factory" in the northern Great Plains. Soils The soils of this cover type are varied. Mollisols occur from the Canadian border to the southern boundary of the cover type in Texas, as do Entisols. Alfisols and Aridisols are less extensive and are mostly in the southern portion. Land Use Large areas of the most productive sites have been converted to crop farming; the remainder is rangeland. Data Source: United States Department of Agriculture, Forest Service THE PRAIRIE COVER TYPE   View/ Download a printable PDF version  Physiography The prairie cover type is relatively large contiguous grassland that lies between the deciduous forests of the East and the short-grass plains of the West, on the flat to rolling hill land of the Central Lowland. Topographic relief delineates the boundaries of this cover type, the 1,500-foot contour being the western boundary and the 500-foot contour being the eastern boundary. The northern limits extend into Canada, and the southern limits extend into southern Texas. Most of the lands of this cover type, excluding those south of the Missouri River, are those of young glacial drifts and dissected till plains. The area south of the Missouri River is older, has well-developed drainage systems, and is flat to rolling hill land. Climate The climate varies widely in this cover type. The length of the frost-free season varies from less than 120 days in the north to almost 300 days in the south. On the east, from Texas to Indiana, the prairie boundary lies close to the 40-inch isohyets. On the west, the southern boundary is near the 30-inch isohyet; further north, the prairie reaches the 20-inch isohyet. In general, more precipitation occurs in the warmer part of the year. During the growing season, the amount of precipitation, on average, varies from 60 percent of potential evaporation in the west to 100 percent in the east. Vegetation The prairie cover type is known to many as the tall-grass or true prairie. Blue stems constitute about 70 percent of the vegetation and reach heights of 5-6 feet in lowland areas. Large numbers of flowering forbs are present but are usually overshadowed by the grasses. Most of the plants are classified as warm-season plants. Woody vegetation is rare. Willow occurs in some places in exceptionally moist areas of the northern part of the cover type, and needle leaved evergreens and broad-leaved deciduous trees are scattered in the southern part. Deciduous trees are common along permanent streams in the eastern portion. Fauna Bison once grazed at the western margin of the tall-grass prairie, and the pronghorn, or antelope, is still present there. Jackrabbits are common residents of the prairie, and cottontails are present where there are streams and cover. Burrowing rodents include ground squirrels, prairie dogs, pocket gophers, and many smaller rodents. Burrowing predators include the badger and the black-footed ferret, now considered an endangered species. The Texas red wolf is classed as an endangered species on the southern border of the cover type. The coyote is still common. The northern portion of the prairie cover type is an important breeding area for a number of species of migrating waterfowl. Many of these migrators winter on the coastal plains of Texas and Louisiana. Mourning doves have become abundant as shelterbelt plantings have developed. Among the gallinaceous birds, the sharp-tailed grouse, greater prairie chicken, and bobwhite are present in fair numbers. The northern greater prairie chicken, however, is considered a rare species, and Attwater's prairie chicken, on the gulf coast of Texas, is listed as an endangered species. Soils The soils of the prairie cover type are primarily Mollisols. There are smaller areas of Entisols and one small area of Vertisols. Most of the soils have dark upper horizons.  Land use  Most of the cover type has been converted to cropland. Data Source: United States Department of Agriculture, Forest Service THE DESERT GRASSLAND COVER TYPE   Physiography The desert grasslands cover type occurs in scattered areas on tablelands of moderate to considerable relief in the Colorado Plateaus province—in Arizona, New Mexico, and Utah and on the plains with low mountains of the Mexican Highland section in southwestern Texas. Elevations range from 5,000-7,000 feet. These tablelands or plateaus are moderately to severely dissected by rugged canyons. Climate The amount of precipitation in this cover type is low, ranging from 8-12 inches annually. Usually more than half falls in the warmer part of the year. During the frost-free season, the evaporation potential is five or more times the normal rainfall. The frost-free season ranges from more than 200 days in Texas to about 120 in Utah. Vegetation The grass life form predominates on these plateaus at intermediate elevations, and shrub life forms are dominant at higher and lower elevations. In transition zones, shrubs give way to galleta to black grama to blue grama. Consociations of these species occur, but almost pure stands are the rule. Tobosa replaces galleta in the southern extensions in Texas of this cover type, and three-awn becomes the dominant in the northern extensions in Utah. In its northern extensions, this cover type is more open grassland with low shrubs. Fauna Pronghorn, or antelope, are the primary larger mammals in the desert grasslands cover type. Mule deer also occur. The coyote and bobcat are among the chief animal predators. They prey on black-tailed jackrabbits, cottontails, wood rats, and a large number of small rodent species, such as the kangaroo rat and the deer mouse. Scaled quail range into the grasslands, especially where brush has made an invasion. Among the smaller birds of the cover type are the horned lark, several sparrows, the loggerhead shrike, and nighthawks. Avian predators include the golden eagle, great horned owl, and various hawks. Soils The soils are almost entirely Entisols that have no pedogenic horizons and Aridisols that lack pedogenic horizons and are never moist for as long as three consecutive months.  Land use  Most of this cover type is used as rangeland. Data Source: United States Department of Agriculture, Forest Service THE AGRICULTURE COVER TYPE   The agriculture cover type includes land used mainly for production of food crops, such as wheat, corn, soybeans, or commodities such as cotton. This cover type is not restricted to a particular climate, physiography, or soils, but occurs where economic conditions are favorable. The best examples of this type are the former prairies of the Midwestern United States, which have been replaced with corn and wheat, the Central Valley of California, where vegetable crops are grown, and the Mississippi basin, where soybeans and other agricultural crops are produced. In other areas, the agriculture cover type is intermixed with natural cover, which provides an idea of natural vegetation that is characteristic of the section. Data Source: United States Department of Agriculture, Forest Service