Chapter 43
Ecological Subregions of the United States

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Southern Rocky Mountain Steppe - Open Woodland - Coniferous Forest - Alpine Meadow

Nine Sections have been delineated in this Province:

These Sections are located in the west-central conterminous States, including parts of New Mexico, Colorado, Utah, Wyoming, Idaho, and Montana. The area of these Sections is about 35,000 mi2 (68,000 km2). Section M331C is not delineated.

Section M331A--Yellowstone Highlands

Geomorphology. The Yellowstone Plateau was formed from two volcanic episodes. Other areas include high rugged mountains with ridges and cirques at higher elevations and narrow to broad valleys. Much of this area has been glaciated,and moraines are common. Elevation ranges from 6,000 to 13,000 ft (1,800 to 4,100 m) in the mountains, and 2,500 to 6,500 ft (763 to 1,983 m) in the basins and valleys. This Section is within the Middle Rocky Mountains physiographic province.

Lithology and Stratigraphy. Precambrian metamorphic and Tertiary volcanic rocks are in this area. Main surface flows consist of silicic rhyolites and welded tuffs. Mafic basalts rim the edge of the plateaus.

Soil Taxa. There are frigid and cryic Ochrepts, Boralfs, and Borolls, with poorly drained Fluvents, Aquolls, and Aquepts in the basins and valleys. These soils are generally shallow to moderately deep, but can be deep in valley areas. Textures are usually medium to moderately coarse with abundant rock fragments.

Potential Natural Vegetation. K\"uchler mapped potential vegetation as wheatgrass--needlegrass--shrubsteppe on drier, lower elevation valleys (55 percent), and Douglas-fir forest and western spruce-fir forest (45 percent) between 5,500 and 9,500 ft (1,667 and 2,879 m). Lodgepole pine is the common cover type, with an understory of grouse whortleberry, pine grass, heartleaf arnica, or Oregongrape. Alpine vegetation, including whitebark pine and subalpine fir, occurs above 9,500 ft (2,878 m). Sheep fescue, alpine bluegrass, and American bistort are common grass and forb species.

Fauna. Birds are typical of the forested portions of the northern Rocky Mountains, including Steller's jay, black-capped chickadee, and pine siskin. This Section boasts a very rich avifauna, including such specialists as white pelican, trumpeter swan, and (black) rosy finch. Other typical species include harlequin duck, Barrow's goldeneye, Swainson's hawk, bald eagle, osprey, sage grouse, sandhill crane, Franklin's gull, American dipper, Townsend's solitaire, yellow-rumped warbler, and Brewer's sparrow. Typical herbivores and carnivores include bison, mule deer, pronghorn, elk, moose, black bear, bobcat, and cougar. Smaller common herbivores include the snowshoe hare and the northern flying squirrel. Rare species include the grizzly bear, gray wolf, wolverine, fringed myotis, pygmy shrew, pygmy rabbit, Preble's shrew, and Uinta chipmunk. Herpetofauna typical of this section are the spotted frog, prairie rattlesnake, rubber boa, boreal toad, and bloched tiger salamander.

Climate. Precipitation ranges from 20 to 45 in (510 to 1,140 mm) annually; most occurs during fall, winter and spring. It occurs mostly as snow above 6,000 ft (1,800 m). Rain is common during the growing season. Climate is cold, moist continental. Temperature averages 35 to 47 oF (2 to 8 oC). The growing season lasts 25 to 120 days; it is less at some higher elevations.

Surface Water Characteristics. Many perennial streams and lakes occur. Ground water supplies are small and mostly untouched. Many lakes and wet meadows are associated with areas above 6,000 ft (1,800 m). Large lakes include Yellowstone Lake, Henry's Lake, Lewis Lake, Island Park Reservoir, and Shoshone Lake. Hot springs are fairly common. Glacial valleys dominate second and higher order streams. There are many short, steep tributaries with high water and sediment delivery efficiencies.

Disturbance Regimes. Historic fire occurrence has been low intensity, low severity, patchy fires and infrequent, high intensity, high severity, continuous fires. Fire suppression has largely reversed this situation. Insect infestations and outbreaks of disease are also an important natural source of disturbance.

Land Use. Timber production and livestock grazing are the dominant land uses. A small amount of forage and other crops are grown in some valleys. The mountains are used for wildlife habitat, watershed, and recreation.

Cultural Ecology. Reserved.

Compiled by Northern Region.

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Section M331B--Bighorn Mountains

Geomorphology. There are high mountains with sharp crests, rolling uplands, and dissected hills, with alpine glaciation dominating the upper third of the area. The rugged hills and mountains are cut by many narrow valleys with steep gradients. Elevation ranges from 4,000 to 13,000 ft (1,220 to 3,962 m). This Section is within the Middle Rocky Mountains physiographic province.

Lithology and Stratigraphy. The central part of the Section is Precambrian quartz monzonite to quartz diorite in the north and Precambrian gneiss in the south. The periphery of the Section is Paleozoic carbonates and shales. A small area in the extreme northeast of the Section is Cretaceous sandstones, siltstones, and shales.

Soil Taxa. Soils include cryic Borolls, Ochrepts, and Boralfs. These soils are generally shallow to moderately deep, but some deep soils occur in alluvial and colluvial basins. Textures are generally loamy or sandy, with large amounts of rock fragments.

Potential Natural Vegetation. K\"uchler mapped potential vegetation as Douglas-fir forest and western spruce--fir forest (50 percent) and wheatgrass--needlegrass--shrubsteppe (50 percent). Common tree species include lodgepole pine, Douglas-fir, subalpine fir, and Engelmann spruce. Idaho fescue, bluebunch wheatgrass, and mountain big sagebrush are common grass and shrub species.

Fauna. Birds are typical of the Rocky Mountains. Species include ferruginous and Swainson's hawks, golden eagle, blue grouse, sage grouse, mountain plover, Steller's and gray jay, Clark's nutcracker, Townsend's solitaire, green-tailed towhee, and western tanager. Species nearing the edge of their ranges are calliope hummingbird, indigo bunting, and clay-colored sparrow. Typical herbivores and carnivores include white-tailed deer, mule deer, elk, moose, pronghorn, black bear, bobcat, and cougar. Smaller common herbivores include the snowshoe hare, yellow-bellied marmot, and the northern flying squirrel. Bison are historically associated with this Section. Herpetofauna typical of this Section are the spotted frog, rubber boa, boreal toad, bloched tiger salamander, and, at lower elevations, the prairie rattlesnake.

Climate. Precipitation ranges from 15 to 40 in (380 to 1,020 mm), with much occurring as spring and fall rains. Climate is cold continental with dry, cold winters. Temperature averages 36 to 43 oF (2 to 6 oC). The growing season lasts 45 to 90 days.

Surface Water Characteristics. This area has medium to fine density dendritic patterns with moderate gradients. Streams are deeply entrenched as they leave the mountains. Lakes occur in glaciated terrain, as well as in high elevation cirques and basins. Major streams include the Tongue, Shell, and Tensleep.

Disturbance Regimes. Fire, insects, and disease are the dominant natural sources of disturbance. Fire has historically been fairly frequent, low intensity, and patchy; however, fire suppression has caused this pattern to change to less frequent, more intense, larger fires.

Land Use. The land is used for timber harvest, livestock grazing, wildlife habitat, watershed, and recreation.

Cultural Ecology. Reserved.

Compiled by Northern Region and Rocky Mountain Region.

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Section M331D--Overthrust Mountain

Geomorphology. This Section occurs within the Middle Rocky Mountain physiographic province. The Overthrust Mountains Section is part of western Wyoming, southeastern Idaho, and north-central Utah. Mountain ranges include the Teton and Salt River Ranges in Wyoming; Snake River, Caribou, Webster, Aspen, Portneuf, Bannock, and Bear River Ranges in Idaho; and the Wasatch Range in Utah. Anticlinal and synclinal structures and thrust fault zones control development of linear valleys and ridges in the northern part of this Section. Some ranges are bound by thrust faults that dip west. Snake River Mountains are distinct, separate, and subparallel. They are mostly steep, rugged mountains with narrow to broad valleys. The Teton Range is the highest in this Section. The Wasatch Range has very steep topography and an extensive and active fault. Higher portions of this Section have been glaciated, with few active glaciers and snow fields in the Teton Range. Many cirques, moraines, and other glacial features are present and extend into Utah. Alluvial fans and mud flow fans have developed at the mouths of many canyons in Utah. Mass movements are common and helped form the Wyoming Range. Elevation ranges from 5,000 to 13,000 ft (1,524 to 3,962 m). Local relief ranges from 3,000 to 7,000 ft (900 to 2,134 m).

Lithology and Stratigraphy. There are Paleozoic and Mesozoic sedimentary rocks. Some Precambrian rock is exposed near Pocatello, Idaho. Sedimentary rocks such as limestones, siltstone, cherts, sandstones, and shales dominate this Section.

Soil Taxa. Soils include Alfisols, Mollisols, Histisols, Inceptisols, and Entisols, in combination with frigid and cryic soil temperature regimes, along with xeric, udic and aquic soil moisture regimes.

Potential Natural Vegetation. K\"uchler vegetation types include lodgepole pine-subalpine forest, and Douglas-fir forest with outer fringes of sagebrush steppe in the northern portion of the Section. Mountain mahogany-oak scrub surrounds a Douglas-fir forest in the Utah portion of the Section. The Soil Conservation Service identifies the potential natural vegetation as mixed conifers and sagebrush-grassland with Douglas-fir, lodgepole pine, and aspen occupying northern aspects. About 50 percent is Douglas-fir forest. Vegetation zones are controlled by a combination of altitude, latitude, slope exposure, and prevailing winds. Areas of alpine tundra exist on highest mountains, subalpine zone has spruce--fir forests, and montane zone has ponderosa pine and Douglas-fir forest. Sagebrush occurs at the lower elevations.

Fauna. This Section was once characterized by bison, bighorn sheep, and large carnivores such as the gray wolf and grizzly bear. These species have been reduced, primarily at the hand of man, to isolated areas within their historic range. Currently, large ungulates include Rocky Mountain elk, mule deer, and moose; cougar and black bear comprise the large predators. Historical and present-day herpetofauna include the western toad and Great Basin spadefoot; spotted and northern leopard frogs; tiger salamander; short-horned and sagebrush lizards; the gopher snake, rubber boa, racer, several species of garter, and the western rattlesnake. Habitats in this Section support a rich and diverse avifauna of neotropical migratory land birds, waterfowl and gallinaceous species. Three subspecies of inland cutthroat trout (Yellowstone, Bonneville, and Colorado) represent the historic salmonid component. In addition to the above cutthroat species, rainbow, brown, brook, and hybrid trout now inhabit most waters.

Climate. Precipitation ranges from 16 to 40 in (400 to 1,016 mm) annually; most occurs during fall, winter and spring. It occurs mostly as snow above 6,000 ft (1,820 m). The semiarid steppe regime is where precipitation falls mostly in the winter, with large amounts falling as snow. Climate is influenced by prevailing winds and the general north-south orientation of the mountain ranges. Summers are dry with low humidity. Precipitation during the frost-free period is 30 to 40 percent of the evaporation potential. Temperature averages 35 to 45 oF (2 to 7 oC), but may be as high as 50 oF (10 oC) in the valleys. The growing season lasts 80 to 120 days.

Surface Water Characteristics. There is a low to moderate frequency of rapidly flowing rivers and streams. Rivers flow into the Great Basin or Snake River drainage. A small area of the Section is drained by the Colorado River. Few lakes and wet meadows are associated with areas higher than 5,000 ft (1,500 m). Large lakes include Bear Lake, Gray's Lake, Palisades Reservoir, and Blackfoot Reservoir.

Disturbance Regimes. After fire, aspen and lodgepole pine replace higher seral species. Mass movements are common and water erosion is occurring.

Land Use. Forest-related industries are important in this Section. Approximately 70 percent of the land is forested and used for timber production and livestock grazing. Mining and oil and gas extraction are also important uses; large reserves of phosphate are in southeast Idaho. Recreation remains very important.

Cultural Ecology. Reserved.

Compiled by Intermountain Region.

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Section M331E--Uinta Mountains

Geomorphology. This Section occurs within the Middle Rocky Mountain province. The Uinta Mountains Section is located in northeastern Utah and the southwest corner of Wyoming. Mountains are an anticlinal uplift with an east-west orientation. Periglacial and glacial processes have shaped higher elevation landforms with freezing and thawing, an active process. At lower elevations, erosion by water and wind are active landforming processes. Elevations range from approximately 6,000 to 13,000 ft (1,800 to 3,900 m). Slopes range from about 5 percent to vertical in gradient.

Lithology and Stratigraphy. Precambian quartzite forms the core of the Uinta Mountains, with inclusions of red pine shale. At lower elevations, there is predominantly Mississippian and Madison limestone; inclusions of Bishop conglomerate, Brown's Park and other minor formations occur.

Soil Taxa. Entisols, Inceptisols, and Alfisols dominate the timbered land. Mollisols occur in the meadows, land vegetated with aspen, sagebrush and grass, and mountain brush sites. Temperature regimes range from mesic to pergelic, and soil moisture regimes are aridic, xeric, and udic.

Potential Natural Vegetation. K\"uchler vegetation types include alpine meadows, Douglas-fir forest, and western spruce-fir forest. It has been noted that some of K\"uchler's vegetation types are incorrect for this Section. More accurate information, from higher to lower elevations, is alpine tundra, Engelmann spruce, spruce-fir, lodgepole pine, subalpine meadow, Douglas-fir, ponderosa pine, aspen, mountain big sagebrush, oak and mountain brush, pinyon-juniper, Wyoming big sagebrush, and cold desert shrub. Douglas-fir is limited to limestone and lower elevations in canyons on quartzite. Oak communities are generally limited to the western portion of the Section. The eastern portion is mostly juniper-pinyon woodland with sagebrush steppe.

Fauna. Mammalian predators include cougar, black bear, coyote, bobcat, red fox, ringtail, and pine marten. Lynx and wolverine occurred historically; both may still occur in small numbers. Once common, bighorn sheep and elk populations were greatly reduced or extirpated in the early 1900's. Bighorn have been re-introduced in a few places, and elk now occur throughout the Section. The presence of Moose is also widespread. Mountain goats have been introduced, their numbers appear to be increasing. Pronghorn antelope are found at lower elevations. River otters were recently re-introduced to portions of the Green River. Small mammals of interest include pika and yuma myotis. Breeding raptors include red-tailed, Cooper's, sharp-shinned, Swainson's, marsh, and ferruginous hawks; kestrel; northern goshawk; flammulated, great horned, short-eared, long-eared, saw-whet, and boreal owls; golden eagle; and prairie falcon. Peregrine falcon and osprey nest along the Green River and Flaming Gorge. Bald eagle and rough-legged hawk winter here. Great gray owls occurred historically, but may not be present today. Sandhill cranes may nest here; whooping cranes and common loons pass through during migration. White-tailed ptarmigan and pheasant have been introduced; blue, ruffed, and sage grouse are native gallinaceous species. Many neotropical migrant land birds breed here. The three-toed woodpecker is common in the Uinta Mountains. Bonneville and Colorado River cutthroat trout are important native species; introduced trout species are present in most lakes and streams. The Green and Yampa Rivers contain proposed critical habitat for four endangered fishes endemic to the Colorado River system Colorado squawfish, razorback sucker, humpback chub, and bonytail chub. Two candidate species, flannelmouth sucker and roundtail chub, also occur here.

Climate. Precipitation ranges from 8 to 35 in (200 to 890 mm) annually. Most precipitation comes in the winter in the form of snow above 9,000 ft. Summer afternoon storms are common in higher elevations. There is a high variability of precipitation at lower elevations; but, generally, summer and winter precipitation is about equal, with some years wet and others dry. Temperature ranges from 28 to 45 oF (-4 to 8 oC). The growing season lasts 20 to 90 days.

Surface Water Characteristics. There is a high frequency of rapidly flowing rivers and streams. Flows from the western portion of the Section are to the Provo River and into the Great Salt Lake. Rivers flow from north to south on the south slope, and from south to north on the north slope. Predominant flows on the south slope join flows from the west and continue south to join the Colorado River. Rivers are glaciated or stream cut, with numerous lakes and wet meadows associated with glaciated areas above 9,500 ft (2,880 m).

Disturbance Regimes. From low to high elevation, alpine fire is probably insignificant. Engelmann spruce has low frequency and small fires (frequency of 300 to 400 years or more and mostly less than 100 acres. In mixed conifers there are more frequent and larger fires than in the Engelmann spruce belt. Lodgepole pine has an 80 to 200 year interval and large fires to 20,000 acres or more. Ponderosa pine has 20 to 50 year interval underburns. Mountain big sagebrush and mountain brush have 20 to 80 year intervals and 10 to 1,000 acres or more in size. Pinyon-juniper has a 20 to 200 year interval with small fires up to 100 acres being common and larger fires being rare. These estimates of fire frequency and size are applicable to presettlement times. In modern times, the national forest fire suppression policy has resulted in reduced fire frequency and size in all timber types. Periodic flooding in the major stream systems occurs in spring with snow melt. Degree of flooding depends on high elevation and mid elevation melt levels and depth of snow. One hundred year and 50 year flooding events have caused extensive damage downstream.

Land Use. Much of the land is set aside for national parks, monuments, and primitive areas. Livestock grazing and timber production are important uses, along with recreation and mining.

Cultural Ecology. Reserved.

Compiled by Intermountain Region.

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Section M331F--Southern Parks and Rocky Mountain Ranges

Geomorphology. Included in the Southern Rocky Mountain Province, this Section is located in northeast-central New Mexico and south-central Colorado. Landforms are mountains and a few valley plains. The Sangre de Cristo Mountains are this Section's major landform feature. Elevation ranges from 7,500 to 14,000 ft (2,300 to 4,300 m).

Lithology and Stratigraphy. There are Precambrian igneous and metamorphic rocks and Cenozoic and Paleozoic sedimentary rocks. A few Cretaceous through Mid-Tertiary intrusive volcanic and volcaniclastic rocks are present.

Soil Taxa. Soils include Glossoboralfs with frigid soil temperature regimes and udic soil moisture regimes, and Cryoboralfs and Cryochrepts with cryic soil temperature regimes and udic soil moisture regimes.

Potential Natural Vegetation. Predominant vegetation includes Douglas-fir and ponderosa pine in frigid soil temperature regimes; Engelmann spruce and subalpine fir in cryic soil temperature regimes; and kobresia, geum and arenaria in alpine pergelic zones.

Fauna. Reserved.

Climate. Precipitation averages 24 to 28 in (600 to 700 mm) annually, with less than half of the precipitation falling during the winter. Temperature averages 32 to 45 oF (0 to 7 oC) and winters are cold. The growing season lasts 70 to 110 days.

Surface Water Characteristics. Water from streams and lakes is abundant and ground water is plentiful.

Disturbance Regimes. Fires vary in frequency and intensity in ponderosa pine stands, but may occur when fuel load is high and dry. Fire is rare in areas with cryic temperature regimes and udic soil moisture regimes. The upper mountain slopes are forested, but merchantable timber is scarce. Recreation, mining, and ranching are important land uses.

Land Use. Reserved.

Cultural Ecology. The Southern Parks and Rocky Mountain Ranges Section is comprised largely of high elevation and very high elevation meadows and mountain ranges, principally the Sangre de Cristo Mountains. High elevation parks and ranges present physical limitations with regard to weather patterns, reduced oxygen levels, lack of abundance and variety in plant and animal communities, and a short growing season. There is little evidence of permanent occupation during prehistoric times, but high elevation areas have been utilized on a relatively limited basis from the earliest dates of human occupation in the Southwest, i.e., since about 12,000 years ago. Although such areas are somewhat inhospitable, prehistoric peoples did make considerable use of various resources found in high elevation areas. These included lithic materials, large and small game, plant materials, spiritual power locations, and various minerals. With heavy reliance on agriculture beginning around 1000 A.D., early farmers began using the lower limits of high elevation areas to grow crops. High elevation areas have the most abundant and most reliable rainfall in the Southwest, which functioned to attract agricultural peoples; but limitations were presented by an increasingly shorter growing season with increase in elevation.

In the earlier portion of the historic period in the 1600's and 1700's high elevation activities included continued hunting and foraging by Native Americans, but with the addition of Anglo fur trapping and Hispanic summer sheep pasturage. As Anglo and Hispanic utilization increased, such activities as hard rock mining, cattle grazing, and timber harvest and freighting grew in importance. These activities were highly dependent on Eastern transportation and market systems. By the late 1800's, more and more farms, ranches, and homesteads made their appearance in the Sangre de Cristo Mountains. Through construction of irrigation systems, supplied with water from the relatively abundant precipitation at high elevations, farmers and homesteaders were able to survive by growing crops to help feed cattle and sheep herds during the harsh winter months. Farms, ranches, and homesteads were generally single-family operations, but a number of small towns, mostly populated by Hispanic peoples, began to spring up. Much of the area within this Section is now national forest land, with a significant portion designated as wilderness. Economic uses of the mountains include recreation, logging, and ranching. Both Hispanic and Native American communities continue many traditional uses of the mountains, and many of the peaks have special religious significance for nearby pueblos.

Compiled by Southwestern Region.

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Section M331G--South-Central Highlands

Geomorphology. Steeply sloping to precipitous mountains are dissected by many narrow stream valleys with steep gradients. Upper mountain slopes and crests may be covered by snowfields and glaciers. High plateaus and steep walled canyons are common, especially in the west. Elevation ranges from 7,545 to 14,110 ft (2,300 to 4,300 m). This Section is within Fenneman and Johnson's Southern Rocky Mountains (eastern half of the Section) and Colorado Plateaus (western half of the Section) geomorphic physical divisions.

Lithology and Stratigraphy. The San Juan Mountains area (eastern half of the Section) is Tertiary volcanic ash flows, lavas, and conglomerates with local porphyritic intrusives. The western half is mostly Pennsylvanian through Cretaceous sandstones, siltstones, shales, and conglomerates, with local carbonates near the San Juan Mountains. In the extreme southern part of the Section is a small area of Tertiary sandstones, shales, and conglomerates.

Soil Taxa. This area has frigid, cryic and pergelic temperature regimes, and aridic, ustic, and udic moisture regimes. Mollisols, Alfisols, Inceptisols, and Entisols are most dominant on the uplands. Great groups and suborder combinations at the higher elevations would include Cryoborolls, Cryochrepts, Cryumbrepts, Cryoboralfs. Haploborolls, Argiborolls, Haplustalfs, and Eutroboralfs are dominant at lower elevations. Valley bottoms and riparian areas will have moist versions (aquic) of Mollisols and Entisols, and certain amounts of Histisols. Valley bottoms often contain Fluvaquents, Cryaquents, Cryaquolls, Haplaquolls, and Borohemists.

Potential Natural Vegetation. Vegetation ranges from shrub and grasslands, forests, and alpine tundra. K\"uchler classified vegetation as southwestern spruce--fir forest; pine--Douglas-fir forest; mountain mahogany--oak scrub; Great Basin sagebrush; juniper-pinyon woodland; and alpine meadows and barren.

Fauna. Elk, mule deer, black bear, and mountain lion are common large mammals of this Section. Rocky Mountain bighorn sheep inhabit higher elevations, and moose have been recently introduced. Smaller mammals include beaver, marmot, snowshoe hare, pine marten, and pika. Common forest-dwelling birds are Steller's jay, grey jay, and Clark's nutcracker, and blue grouse. Mountain bluebird, broad-tailed hummingbird, and Swainson's hawk are typical summer residents. Herpetofauna present include western garter snake, chorus frog, and leopard frog. Native cutthroat trout have been displaced in parts of their former range by brook, rainbow, and brown trout.

Climate. Precipitation ranges from 15 to 30 in (370 to 750 mm). Temperature averages 32 to 45 oF (0 to 7 oC). The growing season last less than 70 days.

Surface Water Characteristics. Water from streams and lakes is abundant. Ground water is plentiful. The Rio Grande, Animas, Gunnison, and San Miguel Rivers flow through here.

Disturbance Regimes. Fire, insects, and disease are principal sources of natural disturbance.

Land Use. More than 50 percent of this area is Federally owned, the remainder is in farms, ranches, and private holdings. Most of the grassland and much of the open woodland is grazed. Some small valleys are irrigated. Recreation, mining, and timber harvest are important land uses.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.

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Section M331H--North-Central Highlands and Rocky Mountain

Geomorphology. This area includes steeply sloping to precipitous flat-topped mountains dissected by narrow stream valleys with steep gradients. High plateaus have steep walled canyons. There are gently rolling mountain parks, mountain ridges, and foothills. Elevation ranges from 5,600 to 12,000 ft (1,706 to 3,657 m). This Section is within three geomorphic physical divisions: Fenneman and Johnson's Wyoming Basin (northern part of the Section), Southern Rocky Mountains (central part of the Section), and the Colorado Plateaus (southern part of the Section).

Lithology and Stratigraphy. The northern one-third of the Section is predominantly Cretaceous sandstones, siltstones, shales, and coals, with local porphyritic intrusives. This part of the Section includes the White River uplift, the northeastern part of which is Tertiary basalt. Much of the remaining two-thirds is structurally complex and includes Lower Paleozoic carbonates and shales and Upper Paleozoic conglomerates, sandstones, siltstones, shales, and evaporites. In the central part of the Section are Precambrian granite and biotite gneiss. In the extreme south are volcanic rocks, including ash flow tuffs, andesitic lavas, breccias, and conglomerates. The lower elevations in the southern two-thirds of the Section are Cretaceous and Tertiary sandstones, siltstones, shales, and local coals. The rock types in this area make it highly susceptible to slope failure. The southern part of the Section also includes local glacial drift and morainal deposits.

Soil Taxa. There are mesic, frigid, and cryic temperature regimes. Soils include Mollisols, Alfisols, Inceptisols, and Entisols, including Boralfs, Borolls, Ochrepts, Orthids, and Orthents.

Potential Natural Vegetation. K\"uchler mapped vetetation as western spruce--fir forest, pine--Douglas-fir forest, juniper--pinyon woodland, mountain mahogany--oak scrub, and sagebrush steppe. Above timberline, alpine tundra predominates. At higher elevations types include Engelmann spruce, subalpine fir, Douglas-fir, ponderosa pine--Douglas-fir, aspen, and meadows of grass and sedge. At lower elevations, there are pinyon pine, shrubs, grass, and shrub-grass vegetation.

Fauna. Elk, mule deer, black bear, and mountain lion are typical large mammals of this Section. Rocky Mountain bighorn sheep inhabit the higher elevations. Common smaller mammals include marmot, beaver, snowshoe hare, pika, and pine marten. Typical forest-dwelling avifauna include Clark's nutcracker, grey jay, northern flicker, and Steller's jay. White-tailed ptarmigan inhabit the higher elevations. Mountain bluebirds are common summer nesters. Herpetofauna include chorus frogs, leopard frogs, and western garter snakes. Native cutthroat trout have been displaced in much of their former range by brook, rainbow, and brown trout.

Climate. Precipitation ranges from 7 to 45 in. (170 to 1,140 mm). Temperature averages 32 to 45 oF (0 to 7 oC). The growing season lasts 70 to 140 days.

Surface Water Characteristics. In the mountains, water from streams and lakes is abundant, and ground water is plentiful. Snowfields exist on upper slopes and crests. Major rivers in this Section include Yampa, White, Colorado, Eagle, Arkansas, Taylor, Gunnison, Crystal, Roaring Fork, and Frying Pan.

Disturbance Regimes. Fire, insects, and disease are the principal sources of natural disturbance.

Land Use. More than 50 percent of the mountain area is Federally owned; the remainder is in farms, ranches, and other private holdings. About 50 percent of the park area is federally owned and is leased to ranchers for grazing of cattle and sheep; the remainder is privately owned ranches. There are some irrigated pastures adjacent to the rivers and streams in the park area. Recreation, mining, and timber harvest are land uses in this Section.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.

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Section M331I--Northern Parks and Ranges

Geomorphology. Steeply sloping to precipitous mountains are dissected by many narrow stream valleys with steep gradients. This area has gently rolling mountain parks and valleys, with some mountain ridges. Rugged hills and low mountains are found in narrow bands along the eastern slopes of the Rocky Mountains. These hills are strongly dissected and in many places are crossed by large streams flowing eastward from the mountains. Elevation ranges from 5,575 to 14,410 ft (1,700 to 4,400 m). This Section is within Fenneman and Johnson's Southern Rocky Mountains geomorphic physical division.

Lithology and Stratigraphy. Most of the Section is Precambrian granite and biotitic, felsic, and hornblendic gneiss. North, south, and middle parks have local Pennsylvanian through Cretaceous sandstones, siltstones, and shales. Between middle and south parks are local Tertiary porphyritic intrusives.

Soil Taxa. This Section has mesic, frigid and cryic temperature regimes. Soils include Mollisols, Alfisols, Inceptisols, and Entisols, including Boralfs, Borolls, Ochrepts, Orthids, Orthents, and Ustolls.

Potential Natural Vegetation. K\"uchler mapped vegetation as alpine meadows and barren, fescue--mountain muhly prairie, sagebrush steppe, juniper-pinyon woodland, and Great Basin sagebrush.

Fauna. Common mammals of this Section are elk, mule deer, black bear, and mountain lion. Rocky Mountain bighorn sheep and isolated mountain goat populations inhabit the higher elevations. Smaller mammals include beaver, marmot, pika, pine marten, and bobcat. Common forest-dwelling birds are Steller's jay, Clark's nutcracker, and grey jay. Wild turkeys are not numerous but are present. At higher elevations, white-tailed ptarmigan are present. Mountain bluebirds and broad-tailed hummingbirds are frequently seen summer residents. Herpetofauna present are western garter snakes and leopard frogs; prairie rattlesnakes live at lower elevations in the eastern part of the Section. Native cutthroat trout have been displaced to a large extent by introduced brook, rainbow, and brown trout.

Climate. Precipitation ranges from 5 to 50 in (120 to 1,120 mm). Temperature averages 32 to 50 oF (0 to 10 oC). The growing season ranges from less than 70 to 160 days.

Surface Water Characteristics. In the mountains, water from streams and lakes is abundant, and ground water is plentiful. Snowfields occur on upper slopes and crests. In the parks, perennial streams originate from snowmelt; by August, these streams are often short of water. Large reservoirs store water for domestic, power, and irrigation uses outside the mountain park area. Major streams cross the foothills area, but elsewhere water is scarce. The Arkansas, North Platte, Laramie, Fraser, Yampa, White, Crystal, Roaring Fork, Frying Pan, and Colorado are major rivers in this Section.

Disturbance Regimes. Fire, insects, and disease are predominate sources of naturla disturbance.

Land Use. About 50 percent of the mountain area is Federally owned; the remainder is in farms, ranches, and other private holdings. About 50 percent of the park area is Federally owned; the rest is private ranches. Less than 20 percent of the foothills area is Federally owned, and about 80 percent is farms and ranches. Irrigation occurs along some rivers and streams in park areas and in some small mountain valleys. Grazing use is heavy, occurring on open mountain woodlands and grasslands, on almost all of the park areas, and on the woodlands and grasslands of the foothills. Recreation, mining, and timber harvest are present and past uses.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.

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Section M331J--Wind River Mountains

Geomorphology. This Section, which occurs within the Middle Rocky Mountain physiographic province, is located in western Wyoming. It has high alpine mountains that have been glaciated. Glacial troughs, cirque headwalls, and floors are common. The highest areas have glaciers covering the mountain tops. Elevation ranges from 6,000 to 13,000 ft (1,800 to 4,100 m).

Lithology and Stratigraphy Areas of orthogneiss and paragneiss with Precambrian granites occur. Precambrian metasedimentary rocks also occur, with Quaternary deposits on the west side.

Soil Taxa. Inceptisols, Mollisols, Histisols, Alfisols, and Entisols are in mostly cryic soil temperature regimes, with some pergelic at higher elevations, along with ustic, udic, and aquic soil moisture regimes. Fluvents and Aquolls occur in the valleys.

Potential Natural Vegetation. K\"uchler vegetation types include lodgepole pine and alpine grasses and forbs. Areas of spruce-firs and Douglas-fir forest occur in this Section.

file:///Z|/WWW/forest/ch43.html#toc" Fauna. This Section was once characterized by bison and large carnivores such as the gray wolf and grizzly bear. These species have been reduced, primarily at the hand of man, yet occasionally are still reported in the area. Currently, large ungulates include Rocky Mountain elk, mule deer, bighorn sheep, antelope, and moose; cougar, black bear, and coyote comprise the large predator component. Historical and present-day herpetofauna include the Wyoming and western toads; spotted and northern leopard frogs; tiger salamander; short-horned and sagebrush lizards; the gopher snake, rubber boa, racer, and several species of garter. Habitats in this Section support a rich and diverse avifauna of neotropical migratory land birds; waterfowl, including trumpeter swans and common loons; raptors, including bald and golden eagles and peregrine falcon; and gallinaceous species. The Colorado River cutthroat trout represents the historic salmonid component. In addition, rainbow, brown, brook, golden, mackinaw, and hybrid trout, plus arctic grayling occurs. Rocky Mountain whitefish, speckled dace, squawfish, and other fish also now inhabit the waters here. Of special note is the Kendall Warm Springs dace, found only in this Section and only in one stream.

Climate. Precipitation ranges from 15 to 100 in (375 to 2,550 mm) annually, increasing with elevation. Most occurs during fall, winter and spring as snow, with many summer rains occurring during the growing season. Temperature averages 34 to 47 oF (2 to 8 oC); lower temperatures occur at the highest elevations. The growing season ranges from 25 to 120 days; higher elevations have 0 to 45 days.

Surface Water Characteristics. Many perennial streams and glacial lakes occur. Ground water supplies are small and mostly untouched. The Section is drained by the Green, Wind, and Sweetwater Rivers. Many lakes and wet meadows are associated with higher areas above 8,000 ft. Large lakes include New Fork, Fremont, Willow, Burnt, and Boulder.

Disturbance Regimes. Mass movements are infrequent, and erosion is occurring from water.

Land Use. All forested areas are used as wildlife habitat, for recreation, wilderness, and as watershed. Timber production is important in small areas of this Section. Livestock grazing is also an important use.

Cultural Ecology. Reserved.

Compiled by Intermountain Region.

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