Chapter 48
Ecological Subregions of the United States

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Intermountain Semi-Desert

Nine Sections have been delineated in this Province:

These Sections are located in the northwestern conterminous States, including parts of Washington, Oregon, California, Nevada, Idaho, Utah, Wyoming, and Colorado. The area of these Sections is about 159,100 mi2 (412,100 km2).

Section 342A--Bighorn Basin

Geomorphology. There are piedmont plains and mountain footslopes with large stream terraces along the Wind-Bighorn River system. Plains are eroded to clay shale bedrock in some places, forming badlands. Elevation ranges from 3,600 to 5,900 ft (1,100 to 1,800 m). This Section is within the Middle Rocky Mountains physiographic province.

Lithology and Stratigraphy. Oligocene, Eocene, and Paleocene sedimentary rocks overlie Precambrian rocks. Soil Taxa. Types include mesic Argids, Orthids, and Orthents. These soils are generally moderately deep to deep with moderately fine to clayey textures.

Potential Natural Vegetation. K\"uchler classified potential vegetation as saltbush-greasewood, wheatgrass-needlegrass-shrubsteppe, and sagebrush steppe. Common species include big sagebrush, gardner saltbush, indian ricegrass, and needleandthread. Black sage and bluebunch wheatgrass are common on areas with shallow soils.

Fauna. Birds are typical of the middle Rocky Mountains, and are very similar to those that occur in Sections M331A and M331B. Other species of note are the ferruginous hawk, golden eagle, sage grouse, burrowing owl, Say's phoebe, sage thrasher, and pygmy nuthatch. Eastern kingbirds near the edge of their range in this Section. Typical herbivores and carnivores include white-tailed deer, mule deer, pronghorn, bobcat, and cougar. Smaller common herbivores are the white-tailed jackrabbit, white-tailed prairie dog, and black-tailed prairie dog. Less common is the black-tailed jackrabbit. The bison and black-footed ferret are historically associated with this Section. Herpetofauna typical of this Section are the Great Plains toad, snapping turtle, spiney softshell turtle, smooth green snake, and prairie rattlesnake.

Climate. Precipitation averages 5 to 9 in. (120 to 230 mm). Temperature averages 45 oF (7 oC). The growing season lasts 120 to 140 days.

Surface Water Characteristics. There are moderate to deeply incised third to fifth order streams with dendritic drainage patterns. Major rivers include the Wind, Bighorn, Greybull, and Shoshone. Deep artesian wells also occur.

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

Land Use. The dominant land use is livestock grazing. About 5 percent of the area is irrigated.

Cultural Ecology. Reserved.

Compiled by Northern Region and Rocky Mountain Region.

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Section 342B--Northwestern Basin and Range

Geomorphology. This area occurs within the Basin and Range physiographic province. Northwestern Basin and Range Section is located in the northern portion of Nevada, southeastern Idaho, and south-central Oregon. It extends into northern Utah also. Nearly level basins and valleys are bordered by long, gently sloping alluvial fans. North-south trending mountain ranges and few volcanic plateaus rise sharply above the valleys. Large alluvial fans have developed at the mouths of most canyons. Elevation ranges from 4,000 to 7,200 ft (1,200 to 2,200 m).

Lithology and Stratigraphy. Pliocene volcanic and shallow intrusive igneous rocks occur, along with andesite, breccias, and basalt flows. Alluvial deposits, playas, marshes, and flat deposits occur in the valleys.

Soil Taxa. There are Aridisols in combination with frigid and mesic soil temperature regimes, along with xeric and aridic soil moisture regimes. Large areas have saline-sodic affected soils.

Potential Natural Vegetation. K\"uchler vegetation types include sagebrush steppe. The Soil Conservation Service identifies the potential natural vegetation as shrub-grass with saltbush-greasewood vegetation.

Fauna. A major migration route for waterfowl crosses this Section. It is characterized particularly by tundra swans, lesser snow geese, American widgeons, and pintail, canvasback, and ruddy ducks, which use the wetlands around interior basin lakes. Sandhill cranes, western snowy plovers, and white-faced ibis nest here. California bighorn sheep and California quail characterize the uplands. Small bands of bison once roamed the margin of Malheur Lake but disappeared prior to white settlement. Rare kit foxes live in the desert lowlands. Pronghorn and mule deer are present. Wolverines are occasionally found. Gray flycatchers, Townsend's solitaires, northern sage sparrows, and broad-tailed hummingbirds are characteristic. Spotted frogs and Malheur shrews are uncommon riparian species. Antelope ground squirrels occupy areas of pale desert soils. Sharptail grouse, once common, are no longer present. Warner Lake suckers, Alvord chubs, and Soldier Meadows desertfish are endemic fishes of interior basin lakes and springs. Lahontan cutthroat trout also characterize this Section.

Climate. Precipitation ranges from 4 to 20 in (100 to 790 mm) annually; mountains receive as much as 20 in annually. Precipitation is evenly distributed throughout fall, winter, and spring, but is low in the summer. Summers are hot and dry and winters are cold and dry. Temperature averages 41 to 50 oF (5 to 10 oC). The growing season ranges from 30 to 140 days.

Surface Water Characteristics. Water is scarce except at higher elevations. Few streams and little water storage occurs in this Section. Large ground water supplies have been untapped. Pyramid Lake is the major lake in this Section.

Disturbance Regimes. Short duration and low intensity brush fires occur due to summer thunderstorms. Water and wind erosion is also occurring.

Land Use. Livestock production is the primary use, with little farming. Some mining has also occurred.

Cultural Ecology. Reserved.

Compiled by Intermountain Region.

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Section 342C--Owyhee Uplands

Geomorphology. This area occurs within the Columbia Plateau physiographic province, also known as the Columbia Intermontane province. The Owyhee Uplands Section is part of southwest Idaho, southeast Oregon, and northern Nevada. This area is an uplifted region with doming and block-faulting common. It is deeply dissected from erosional processes. Lavas are older than that of the Snake River Plains. The Owyhee Mountains are made of granite; however, most of the uplands are rhyolites and welded tuffs with silicic volcanic flows, ash deposits, and wind-blown loess. Elevation ranges from 4,000 to 8,000 ft (1,200 to 2,500 m).

Lithology and Stratigraphy. Miocene basalt rocks occur here. Rhyolites, welded tuffs, and silicic volcanic flows are also found in this Section. Columbia basalts occur along the Snake River.

Soil Taxa. Aridisols, Entisols, Alfisols, Inceptisols, and Mollisols occur in combination with mesic and frigid soil temperature regimes, and xeric and aridic soil moisture regimes. Cryic temperature regimes occur at higher elevations.

Potential Natural Vegetation. K\"uchler vegetation types are sagebrush steppe with {\it Artemisia} and {\it Agropyron} and small areas of wheatgrass-bluegrass. The Soil Conservation Service identifies the area as having a sagebrush-grass potential natural vegetation.

Fauna. A major migration route for geese crosses this Section, and it is used particularly by the intermountain population of Canada geese. This Section also is a major wintering area for mallards and common mergansers. California bighorn sheep live in rocky canyons. Gray flycatchers, northern sage sparrows, and mountain quail live in the sagebrush and juniper uplands. Wolverine once lived here but have not been seen for decades. Once common, sharptail grouse are scarce in grasslands and sagebrush foothills. Spotted frogs have been found here. Small bands of elk roam the uplands year-round, and elk from surrounding Sections winter here. Pronghorn, mule deer, and sage grouse inhabit this Section. Remnant bull trout populations are found in cold headwater streams. Other Columbia and Snake River system species include northern squawfish, biglip sucker, bridgelip sucker, Utah sucker, and Columbia redside shiners.

Climate. Precipitation ranges from 7 to 15 in (200 to 400 mm) annually; it is close to evenly distributed throughout the year, but is low from mid summer to early autumn. Precipitation is only 20 percent of the evaporation potential during the frost-free period. Summers are dry with low humidity. Temperature averages 35 to 45 oF (2 to 8 oC). The growing season ranges from 90 to 120 days but is less than 60 days at higher elevations.

Surface Water Characteristics. Water supply from precipitation and streamflow is small and unreliable, except along the Owyhee, Bruneau, and Humboldt Rivers. Snow accumulation at the higher elevations contributes to streamflow. Few small lakes and reservoirs are found in this Section.

Disturbance Regimes. After fire, grasses and forbs replace higher seral species. Water and wind erosion is also occurring.

Land use. Livestock grazing, and dryland and irrigated farming are the major land uses. Recreation is also important.

Cultural Ecology. Reserved.

Compiled by Intermountain Region.

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Section 342D--Snake River Basalts

Geomorphology. This area occurs within the Columbia Plateau physiographic province, also known as the Columbia Intermontane province. The Snake River Basalts Section is part of southeast and south-central Idaho. Most of this Section is characterized by nearly horizontal sheets of basalt laid down in the Snake River drainage to form a plain. Lava flows range from less than 100 ft thick to several thousand ft thick. Block-faulted mountains are also included in this Section. The basalts are mainly two ages: the older flows are of the Miocene and Pliocene epoch; the younger lavas are Pliocene through Recent. The Section is about 60 mi wide and is essentially flat; however, the eastern portions of the Section are much higher in elevation. The surface is a youthful lava plateau with a thin wind-blown soil layer covering it. Shield volcanoes, cinder cones, and squeezed-up lava ridges are common. Craters of the Moon National Monument is an example of the recent volcanic features. Elevation ranges from 3,000 to 6,000 ft (900 to 2,000 m). Lava plain and hills are nearly level to steeply sloping.

Lithology and Stratigraphy. Miocene and Pliocene basalt rocks are present. Sedimentary rocks interbedded with older basalt flows are in the western portion of the Section.

Soil Taxa. Aridisols, Entisols, and Mollisols occur in combination with mesic and frigid soil temperature regimes, along with xeric and aridic soil moisture regimes.

Potential Natural Vegetation. K\"uchler vegetation types include sagebrush steppe with {\it Artemisia} and {\it Agropyron}. The Soil Conservation Service identifies the area as having a sagebrush-grass potential natural vegetation.

Fauna. This Section was once characterized by bison and bighorn sheep, and large carnivores such as the grizzly bear and gray wolf. 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 pronghorn. Cougar, bobcat, black bear and coyote constitute a portion of the predator component. Historical and present-day herpetofauna include the western toad, Great Basin spadefoot; short-horned and sagebrush lizards; and the gopher snake, rubber boa, racer, and several species of garter snakes. Habitats in this Section support a rich and diverse avifauna of neotropical migratory land birds, waterfowl, and gallinaceous species. Three mammalian species, the yellow pine chipmunk, Great Basin pocket mouse, and the dark phase pika, are endemic to this Section. Lava tubes provide roosting, hiburnacula, and nursery habitat for several species of bats. Salmonid species include rainbow, brown, and brook, as well as hybrid trout.

Climate. Precipitation ranges from 5 to 12 in (127 to 305 mm) annually; it is evenly distributed throughout the fall, winter, and spring, but is low in the summer. Precipitation is only 20 percent of the evaporation potential during the frost-free period. Summers are dry with low humidity. Temperature averages 40 to 58 oF (4 to 13 oC). The growing season ranges from 60 to 165 days, decreasing from west to east and with elevation.

Surface Water Characteristics. Low to moderate precipitation provides enough water for dry farming on the outer foothills. Rivers and streams flow into the Snake River drainage. Few lakes and reservoirs are located in this Section. Large lakes and reservoirs include American Falls reservoir, Mud Lake, and Lake Walcott.

Disturbance Regimes. After fire, grasses and forbs replace higher seral species. Water and wind erosion is also occurring.

Land use. Livestock grazing and dryland and irrigated farming are the major land uses. Recreation is also important.

Cultural Ecology. Reserved.

Compiled by Intermountain Region.

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Section 342E--Bear Lake

Geomorphology. This area occurs within the Middle Rocky Mountain physiographic province. The Bear Lake Section is located in the southeast corner of Idaho, southwest corner of Wyoming, and northern corner of Utah. Steep north-south oriented mountain ranges with broad linear valleys are the major landforms. Few areas have been glaciated and were mostly formed from thrust and faults, landslides, and pluvial action.

Lithology and Stratigraphy. There are Eocene continental deposits, mostly sedimentary rocks. Some Eocene lacustrine deposits occur in Wyoming.

Soil Taxa. Alfisols, Mollisols, Histisols, Inceptisols, and Entisols occur 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 and Doulgas-fir forests, with outer fringes of sagebrush lands. Oak-pine forests occur in the Utah portion of this 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.

Fauna. This Section was once characterized by bison, elk, deer, and pronghorn, with carnivores such as grizzly bear, gray wolf, coyote, and mountain lion. These species have been reduced, primarily due to man. The grizzly bear and gray wolf have been extripated from the area. Currently, large ungulates include elk, deer, pronghorn, and moose. Coyote, fox, mountain lion, and some black bear make up the main predator species. Historical and present herpetofauna include western rattlesnake, garter snake, leopard frog, chorus frog, and short horned and sagebrush lizards. Habitats in this Section support many neotropical migratory land birds, waterfowl, raptor, and gallinaceous species. Bonneville cutthroat trout represent the historic salmonids and may exist in isolated areas today. Other aquatic species include brown, brook, and rainbow trout.

Climate. Precipitation ranges from 16 to 40 in (400 to 1,000 mm) annually; most occurs during fall, winter and spring. Precipitation occurs mostly as snow above 6,000 ft (1,800 m). Rain on snow is common. Summers are dry with low humidity. Winter precipitation patterns account for large snow accumulations. Temperature averages 34 to 48 oF (1 to 9oC). The growing season ranges from 50 to 180 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 higher areas above 5,000 ft (1,500 m). Large lakes include Bear Lake, Gray's Lake, Palisades Reservoir, and Blackfoot Reservoir.

Disturbance Regimes. A few high intensity, short duration burns of shrubs occur in the summer due to thunderstorms. Water and wind erosion occurs.

Land Use. Grazing is the major land use, with agricultural crop production also being important. Watershed and recreation are also an significant uses.

Cultural Ecology. Reserved.

Compiled by Intermountain Region.

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Section 342F--Central Basins and Hills

Geomorphology. Plains eroded to clay shale bedrock, creating badlands. Mountain ranges include steep slopes that rise sharply from desert basins. There are alluvial fans, piedmont plains, and piedmonts that slope from the mountains to stream terraces of the Wind-Bighorn system, and to broad intermountain basins. Rugged hills and low mountains are cut by narrow valleys with steep gradients. Broad flood plains are associated with some of the major rivers. Elevation ranges from 3,610 to 10,170 ft (1,100 to 3,100 m). This Section is within Fenneman and Johnson's Wyoming Basin geomorphic physical division.

Lithology and Stratigraphy. The northern half of the Section is Tertiary sandstones, siltstones, and shales. The southern half of the Section is Cretaceous through Tertiary sandstones, siltstones, shales, conglomerates, and local coals. The middle part of the Section also includes local Precambrian granite and metamorphosed sedimentary and volcanic rocks and Precambrian granite and Paleozoic carbonates in the Seminole Mountains.

Soil Taxa. There are mesic and frigid temperature regimes. Soils include Mollisols, Inceptisols, Aridisols, and Entisols, including, Argids, Orthents, Borolls, and Fluvents.

Potential Natural Vegetation. Vegetatative communities range from grass to grass-shrub to shrub-grass to forest. K\"uchler mapped vegetation as sagebrush steppe (sagebrush-wheatgrass); wheatgrass-needlegrass shrub steppe; grama-needlegrass-wheatgrass prairie; and Douglas-fir forests.

Fauna. Typical large mammals of this Section are mule deer, white-tailed deer, elk, and mountain lion. Smaller common mammals are jackrabbit, red fox, swift fox, porcupine, and bushy-tailed wood rat. Year-round forest dwelling bird species include the pygmy nuthatch, red-breasted nuthatch, black-capped chickadee, and Cooper's hawk. Summer residents include sharp-shinned hawk, belted kingfisher, chipping sparrow, and swallow. Representative herpetofauna are the prairie rattlesnake, wandering garter snake, snapping turtle, spiney softshell turtle, boreal chorus frog, and Great Plains toad.

Climate. Precipitation ranges from 5 to 30 in (120 to 750 mm). Temperature averages 39 to 52 oF (4 to 11 oC). The growing season ranges from 80 to 140 days.

Surface Water Characteristics. Water is scarce in some areas. The Wind, Bighorn, South Fork of the Powder, Little Medicine Bow, North Platte, Laramie, and Sweetwater Rivers flow through here. Deep artesian wells exist in the eastern Bighorn basin. Small and intermittent streamflow occurs in some areas. Ground water is meager or lacking in most areas, but is abundant in the fill in some of the valleys of the northern foothills.

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

Land Use. About 50 percent of this area is Federally owned, and 50 percent is in farms and ranches. Most of the land is used for sheep and cattle grazing. About 5 percent of the area is irrigated; often these are small tracts in isolated valleys or along major streams. Some open woodlands at high elevations support logging activities. About 20 percent of the area is in dry crops.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.

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Section 342G--Green River Basin

Geomorphology. This Section includes rugged hills and low mountains, with narrow valleys having steep gradients. Broad flood plains and fans are present on major rivers. Alluvial fans, piedmont plains, and piedmont slopes from the surrounding mountains join to form broad intermountain basins. Elevation ranges from 3,610 to 7,875 ft (1,100 to 2,400 m). This Section is within Fenneman and Johnson's Wyoming Basin geomorphic physical division.

Lithology and Stratigraphy. Most of the Section is Tertiary conglomerates, sandstones, siltstones, and shales, with local Quaternary dune sands and loess. In the eastern quarter of the Section on the Rock Springs uplift, there are Cretaceous sandstones, siltstones, conglomerates, shales, and local coals.

Soil Taxa. The temperature regime is frigid. Soils include Mollisols, Aridisols, and Entisols, including Borolls, Orthents, Fluvents, and Argids.

Potential Natural Vegetation. Vegetative communities include grasses to grass-shrub to forests. K\"uchler classified potential vegetation as sagebrush steppe (sagebrush-wheatgrass), saltbush-greasewood, and wheatgrass-needlegrass shrubsteppe.

Fauna. Pronghorn use parts of the sagebrush ecosystem as rangeland throughout the year. Mule deer prefer to use sagebrush rangeland only during the winter. The Utah prairie dog is an endangered species of this ecosystem. Other mammals that use this ecosystem are the Great Basin coyote, black-tailed jackrabbit, pygmy cottontail, Ord's kangaroo rat, and the Great Basin kangaroo rat. Bird populations are low during the breeding season, averaging only about 25 per 100 acres. The major birds include the marsh hawk, red-tailed hawk, Swainson's hawk, Cooper's hawk, golden eagle, bald eagle, prairie falcon, burrowing owl, and the long-eared owl. The sage grouse and chukar are the important game birds found in this ecosystem. The fauna that are found in the desert shrub ecosystem (saltbush-greasewood community) are the cactus mouse, long-tailed pocket mouse, desert kangaroo rat, black-tailed jackrabbit, and the antelope ground squirrel.

Climate. Precipitation ranges from 7 to 20 in (150 to 500 mm). Temperature averages 39 to 52 oF (4 to 11 oC). The growing season ranges from 80 to 125 days.

Surface Water Characteristics. Water is scarce, but some major rivers and small streams flow through here. Generally, ground water is meager or lacking in most areas, but it is abundant in the fill in some valleys. The Green and Lower Snake Rivers flow through here. Part of the Flaming Gorge Reservoir lies in this Section.

Disturbance Regimes. Primary sources of disturbance are fire, insects and disease.

Land Use. About 80 percent of the area is in farms or ranches. About 50 percent of the area is grazed by sheep and cattle. Many of the valleys and tracts along a few large streams are irrigated, but they make up only 1 to 5 percent of the total area. About 20 percent of the area is dry farmed.

Cultural Ecology. Reserved.

Compiled by Rocky Mountain Region.

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Section 342H--High Lava Plains

Geomorphology. This area includes moderately dissected mountains and broad flat uplands. This Section is dominated by debris slides, rock fall and slow creep erosion processes on slopes of 20 to 120 percent. Some ancient lake terraces occur along the valley sides on slopes less than 30 percent. A multitude of young eruptive events have left volcanic features. During glacial stages numerous large lakes formed, filling to the playas found today. Elevation ranges from 2,000 to 5,000 ft (700 to 1,700 m). Local relief is mostly 300 to 800 ft (90 to 242 m).

Lithology and Stratigraphy. There are Eocene, Oligocene, and Miocene basalts with minor tuffs, sandstone, and siltstone. The Section is predominately underlain by a Columbia River basalt group equivalent. Extensive playas are filled in with fluvial sediments and volcanic ash.

Soil Taxa. Soils in this Section are warm (mesic soil temperature regime) and dry (aridic and xeric soil moisture regimes). They vary in depth to the underlying bedrock and the influence of volcanic ash. In the southern part, there are soils with thin, dark topsoil (Xerollic Camborthids), and some with volcanic ash (Vitrixerandic Camborthids). Other soils with thin, dark topsoil have a cemented hardpan that impedes roots, and a clay-enriched subsoil without volcanic ash (Xerollic Durargids) or with volcanic ash (Vitrixerandic Durargids). Shallow, sandy soils (Lithic Torripsamments) also occur in this part. In other parts of this Section, most soils have thick, dark topsoil and clay-enriched subsoil (Lithic, Aridic and Aridic Calcic Argixerolls, and Aridic Palexerolls); some of these soils also contain volcanic glass (Vitritorrandic Argixerolls).

Potential Natural Vegetation. K\"uchler vegetation is characterized by three principal groups. Sagebrush-steppe ({\it Artemesia-Agropyron}) is considered dominant; followed by the juniper-steppe woodland ({\it Juniperus-Artemesia-Agropyron}) type; least common is wheatgrass-bluegrass ({\it Agropyron-Poa}). More recent classifications reveal a somewhat different characterization. A savanna with ponderosa pine occurs along the extreme western edge of this Section. Proceeding east, western juniper forms a woodland mixed with native sagebrush, bitterbrush and bunchgrasses. This woodland dominates the landscape over much of the western one-third of the Section. The woodland character soon changes as one proceeds east, with sagebrush and bunchgrasses dominating the undulating land; western juniper becomes restricted to rocky outcrops and other areas that have not experienced a recent fire. The eastern portion of the Section maintains a vegetative dominance of sagebrush and bunchgrass, but elements of either the desert or salt desert shrub communities are noticeable. Locally, grasses, sedges, rushes, and forbs occupy wet sites in meadows and along streams.

Fauna. Mule deer and antelope typify the herbivorus component of this Section. Rocky Mountain elk, a recent invader, is now found in the Section in sustained isolated populations. Sage grouse, once common, is now restricted from its original distribution. Valley quail and chukar, introducted species, are found in sustained huntable populations. The Rio Grande turkey, very recently introduced, is now common in isolated populations. Prairie falcon, black-tailed jackrabbit, marmot, badger, and ground squirrel are common small mammals. Magpie, raven, golden eagle, and goshawk are common members of the avian component. Pocket gopher is a common fossorial mammal.

Climate. Precipitation averages 7 to 14 in (180 to 360 mm). Average annual air temperature is 40 to 57 oF (4 to 13 oC). The growing season ranges from 50 to 200 days

Surface Water Characteristics. Streams are infrequent and many are intermittent. Occasional wet meadows, springs, and seeps occur.

Disturbance Regimes. Prior to fire protection, fire was a common disturbance factor. Periods were about 15 to 30 years.

Land Use. Land use is dominantly ranching, including grazing of domestic livestock; other uses include irrigated agriculture, dispersed recreation, and rural communities.

Cultural Ecology. Humans have occupied the Blue Mountains and High Lava Plains Section for at least 12,000 years. This region exhibited prehistoric lifestyles that were transitional between Great Basin cultural patterns to the south and Columbia Plateau cultural patterns to the north. Root digging, seed and berry gathering, hunting, and fishing were the primary economic activities; their relative importance shifted with changing climatic conditions. Peoples tended to live in groups comprising a couple of families during much of the year to utilize resources that were scattered over the landscape and which ripened at different times. Several such groups would come together seasonally at camps on rivers, streams, or large upland meadows to exploit concentrated resources and utilize stored resources. Burning was practiced to improve the production of berries, big game forage, and to drive game. Extensive deposits of obsidian and basalt were intensively used, and these materials were re-distributed widely. Euro-American settlement and exploitation of the area began in the mid 1800's and intensified during the 1860's with the discovery of gold. Locally heavy alteration to the landscape and hydrology occurred due to hydraulic mining and attendant ditch building and use; later these operations were followed by hardrock mining and dredging. Mineral extraction and activities related to improved transportation systems and agriculture led to relatively large settled human populations. Logging, railroad construction, cattle and sheep grazing, and fire suppression have also played a significant role in alteration of the environment. Historic uses of the land created ecological effects on plant and animal species and other resources that far exceed those from prehistoric times.

Compiled by Pacific Northwest Region.

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Section 342I--Columbia Basin

Geomorpholgy. The Section is characterized by generally flat-lying basalt flows. It is a large dissected plain high above sea level. Structurally the Plateau is a great basin between the Rockies and the Cascades. Also, it is the best known example of plateau flood basalts. Channeled scablands, the result of mega-floods, range from excavated low points to coulees miles wide and hundreds of ft deep. Deposits of glacial till, glacial moraine, or glacial outwash blanket the plain. Rolling hills of loess cover unglaciated areas to the south and east. Elevation ranges from less than 200 ft near the Columbia River to more than 4,500 ft on high ridges and low mountains (70 to 1,500 m).

Lithology and Stratigraphy. There are extensive cyclic Miocene basalt deposits, with layers ranging generally from a few dozen to a hundred ft thick. The entire deposit may total over 15,000 ft (4,545 m) deep. Interflow baked soil horizons are common and may reach 5 ft (1.5 m) thick. Older buried rocks include Precambrian marine sediments, Permian through Jurrassic marine sediments, and submarine volcanics and Cretaceous granites. Glacial floods during the Pleistocene deeply eroded the basalt plateau, leaving giant gravel bars, alluvial aprons, and ephemeral lake deposits. Where not removed by floods, loess may overlie basalts from 0 to 200 ft (0 to 60 m) thick.

Soil Taxa. In this Section, soils are mostly warm (mesic soil temperature regime) and dry (aridic soil moisture regime). They formed in parent materials resulting from erosion and re-deposition by great floods and strong winds across the relatively level lava plateau. Volcanic ash deposited in this area has been mostly eroded and mixed with other material, thereby removing and diluting the ash influence in soils. Loess of varying thickness blankets most of this Section. In the central part, there are soils formed in eolium ranging from coarse to silty and in sandy eolium. They overlie sandy glaciolacustrine materials (Xeric Torripsamments and Xeric Torriorthents). These eolium soils also overlie very gravelly and cobbly glaciofluvial materials or fine-textured slack water deposists (Xerollic Camborthids, Aridic and Calciorthidic Haploxerolls).

In the northeastern part, loess hills are dissected by channeled scablands. Soils on the loess hills formed in mostly deep coarse-textured loess (Xerollic Camborthids), some with dark topsoil and lime-enriched subsoil (Calciorthidic Haploxerolls), and with clay-enriched subsoils (Aridic Calcic Argixerolls). On ancient erosion surfaces these are soils with water and root-impeading hardpans, and dark topsoil (Xerollic Durorthids, Durixerollic Camborthids, and Orthidic Durixerolls).

Soils on the flood-scoured, channeled scablands are similar to soils on the highly dissected lava benches in the western part of the Section. Shallow, stony soils (Lithic Camborthids, Haploxerolls, and Argixerolls) formed in loess. Cobbly and stony material from the basalt occur in a complex pattern with moderately deep soils (Xerollic Camborthids, Aridic Haploxerolls, and Argixerolls) formed in loess.

In the southern part, soils are moist except in summer months (xeric soil moisture regime). Soils commonly have dark, organic matter-rich topsoil; some are shallow to bedrock (Lithic Haploxerolls and Argixerolls); some have lime-enriched and clay-enriched subsoils (Typic or Calcic Argixerolls, and Calcic Haploxerolls); and some have thick dark topsoil (Pachic Haploxerolls and Argixerolls). An influence of volcanic ash is recognized in some soils (Vitrandic Argixerolls and Vitrandic Haploxerolls) in this part of the Section.

Potential Natural Vegetation. According to K\"uchler, the sagebrush-steppe is dominant, followed by fescue-wheatgrass and wheatgrass-bluegrass.

Fauna. Large herbivores are represented by a restricted distribution of mule deer and antelope. Coyote, black-tailed jackrabbit, cottontail rabbit, marmot, badger, and several ground squirrels compliment the small mammal component. Western rattlesnake, bullsnake, pond turtle, and several species of lizard are common. Marsh hawk, kestrel, red-tailed hawk and golden eagle are common avian components. Cold water streams and lakes are inhabited by rainbow trout, and introduced Centrarchids are common in reservoirs.

Climate.Precipitation averages 7 to 18 in (180 to 450 mm). August through November is dry. Humidity is low year round. Temperature averages 40 to 57 oF (4 to 14 oC) The growing season ranges from 100 to 200 days.

Surface Water Characteristics. A few rivers and streams are weakly to moderately incised. The Columbia River is the major surface water and includes several major reservoirs. Wetlands and marshes are extensive, but many have been drained for agriculture.

Disturbance Regimes. Wind is the principal disturbance feature. Composition and successional sequences of some communities have changed because of agricultural practices and the introduction of animal species into the valleys.

Land Use. Both dryland and irrigated agriculture dominate. Several specially designated areas are within the Section, including a military training site, two Native American reservations, a wildlife refuge, and Hanford nuclear reservation. A variety of communities are dispersed throughout and range from small rural developments to moderately large urban centers.

Cultural Ecology. Humans have occupied the Columbia Plateau and Okanogan Highlands Sections for at least 12,000 years. For the last 5,000 years, groups spent much of the year in river-oriented pithouse villages of 30 to 300 people. Hunting, salmon fishing, and root and berry collecting were the primary economic activities. They were also the backdrop for much of the social organization and spiritual beliefs. Hunting and fishing were important not only for the sustenance they provided, but for where, when, and how they were carried out. Burning (both intentional and otherwise) to improve plant growth for berry crops and big game forage was common; however, hunting pressure prior to nuro-American settlement may have contributed to the extinction of the Columbia Basin bison population (never a large population at any time in prehistory). Large pithouse villages with between 30 and 200 pit depressions have created small-scale localized ecological effects. Euro-American settlement and exploitation of the area began in the mid 1800's and intensified between 1875 and 1925. Historic activities include lumbering (especially in the Okanogan Highlands), railroad construction, dam building, grazing, wheat ranching, and irrigated farming. These activities have all created ecological effects on plant and animal species and other resources that far exceed most of those from prehistoric times.

Compiled by Pacific Northwest Region.

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