).
Treasure Valley (12a) The
Treasure Valley ecoregion (named for the
Treasure Valley) is an
unglaciated rolling valley containing many
canals and incised rivers. Elevation varies from 2,000 to 2,800 feet (640 to 853 m). The valley is underlain by
Quaternary alluvium,
loess,
lacustrine, and
alluvial fan deposits. Soils have an
aridic moisture regime, and they originally supported
sagebrush-
grassland before the valley was converted to agriculture. Canals and diversions in this portion of the Snake River Plain supply water to
pastureland and
cropland as well as
municipalities. Surface
water quality has been significantly affected by channel alteration, dams, irrigation diversions, irrigation return flow, and
agricultural pollution. Crops include
wheat, sugar beets, alfalfa, potatoes, and
onions.
Population density is greater than in neighboring,
rangeland-dominated ecoregions.
Crop diversity is greater, temperatures are warmer, and the mean
frost-free season is longer than in the Upper Snake River Plain and the Magic Valley. Vegetation outside of agricultural areas is characterized by
Wyoming big sagebrush,
basin big sagebrush,
bluebunch wheatgrass,
bluegrass,
basin wildrye,
Thurber's needlegrass,
rabbitbrush, and
cheatgrass. In
saline areas,
shadscale, greasewood, and
saltgrass occur. The region covers in Idaho and in Oregon, where the
Payette,
Boise,
Weiser,
Malheur and
Owyhee rivers converge into the Snake. It includes lowland areas from
Boise to
Vale and contains the
Deer Flat National Wildlife Refuge.
Lava Fields (12b) The
Lava Fields ecoregion contains
basalt flows,
cinder cones, and
spatter cones rising from irregular plains, at an elevation of 3,800 to 5,500 ft (1,158 to 1,676 m). Exposed basalt or very shallow loessial soils over
volcanics are characteristic.
Surface water availability is extremely limited, and the region is either
barren or sparsely covered by hardy
shrubs and
grasses, including basin sagebrush,
mountain sagebrush, Wyoming big sagebrush, rabbitbrush, bluegrass, bluebunch wheatgrass,
bottlebrush squirreltail, Thurber needlegrass, and
Indian ricegrass. Livestock
carrying capacity is low. The region covers in Idaho in pockets of the eastern Snake River Plain, including
Craters of the Moon National Monument and parts of the
Idaho National Laboratory.
Camas Prairie (12c) The
Camas Prairie ecoregion is a cold, wet valley containing nearly level to rolling
terraces,
bottomlands,
basalt plains, and, on the periphery, alluvial fans. Elevation varies from 4,700 to 5,100 ft (1,443 to 1,554 m). It is flanked by the semi-arid
foothills of the Snake River Plain and the
Idaho Batholith, which trap
mountain runoff on the prairie. Resultant wet soils and
flooding occur and are local and seasonal problems. Frigid
mollisols are common and are colder than the soils of the lower Treasure Valley. Wet
bottomlands support
rushes,
sedges,
meadow grasses, and
willows. Alluvial fans and terraces are covered by bluebunch wheatgrass,
Idaho fescue, bluegrass, basin big sagebrush, and mountain sagebrush. Lava plains support alkali sagebrush, bluegrass, squirreltail, and Idaho fescue. The region covers in Idaho along the
Camas River and is used for small grain and alfalfa farming, pasture, range, and
wildlife habitat.
Dissected Plateaus and Teton Basin (12d) The
Dissected Plateaus and Teton Basin ecoregion is characterized by
dissected plateaus, alluvial fans, low terraces, bottomlands,
outwash plains, and nearly flat, poorly drained
basins. Elevation varies from 4,700 to 6,300 ft (1,443 to 1,920 m). Mollisols developed in thick loess deposits or alluvium and are subject to
wind erosion. Loess is far more extensive than in the Upper Snake River Plain subregion. Sprinkler-irrigated land supports potatoes, alfalfa, and pasture; however, surface irrigation is far less common than in the Upper Snake River Plain.
Non-irrigated land grows small grains. Potential natural vegetation is sagebrush steppe, with mountain big sagebrush,
threetip sagebrush, bluebunch wheatgrass, bluegrass, Idaho fescue, and cheatgrass.
Wet meadows occur in the poorly drained, relatively cold
Teton Basin. The region covers in Idaho in the farthest eastern reaches of the Snake River Plain, approaching the
Teton Mountains. It includes portions of the
Caribou-Targhee National Forest.
Upper Snake River Plain (12e) The
Upper Snake River Plain ecoregion is characterized by nearly level river terraces, floodplains, and lake plains containing many canals and rivers. Elevation varies from 4,400 to 5,000 ft (1,341 to 1,524 m). The region is primarily used for irrigated cropland, pastureland, suburban and urban developments, and industrial areas, and aquatic resources have been degraded by irrigation diversions, channelization, dams,
sewage treatment,
nonpoint pollution,
food processing, and
phosphate processing. Extensive surface-irrigated small grain, sugar beet, potato, and alfalfa farming occurs. The frost-free season is shorter and crops are less varied than in agricultural areas downstream. Potential natural vegetation is sagebrush steppe, with saltbush-greasewood communities in the southwest. Big sagebrush, bluebunch wheatgrass, bluegrass, cheatgrass, rabbitbrush, squirreltail,
needle-and-thread, Indian ricegrass, and
fourwing saltbush are present. Riparian areas feature sedges, perennial grasses, willows, and
cottonwood. The region covers in eastern Idaho, mostly along the
interstate corridor from
American Falls to
St. Anthony. It includes the
Camas National Wildlife Refuge and most of the
Fort Hall Indian Reservation.
Semiarid Foothills (12f) The
Semiarid Foothills ecoregion consists of foothills, alluvial fans, hills, and valleys that separate the Snake River Plain from the
Idaho Batholith ecoregion to the north. At an elevation of 2,900 to 6,500 feet (884 to 1,981 m), it is higher and more rugged than neighboring regions in the Snake River Plain. Shallow,
clayey soils are common, supporting sagebrush steppe communities of bluebunch wheatgrass, bluegrass, Idaho fescue, big sagebrush,
bitterbrush,
medusahead wildrye, and cheatgrass, with bunch grasses, sedges, rushes, and
clovers in wetter areas. Land use is primarily livestock grazing and is distinct from the irrigated agriculture of the Treasure Valley. Wildfire frequency is high. The region covers in two separate areas of Idaho, one northeast of
Weiser in the
Weiser River drainage and one northeast of
Mountain Home, including
Bennett Mountain and nearby hills.
Eastern Snake River Basalt Plains (12g) The
Eastern Snake River Basalt Plains ecoregion is a large irregular plain at an elevation of 3,700 to 6,400 ft (1,128 to 1,951 m), with shallow, stony soils that are unsuitable for cultivation. Only small areas have soils deep enough to be farmed under sprinkler irrigation. Rangeland is widespread and contrasts with the cropland of other subregions in the Snake River Plain. Potential natural vegetation is mostly sagebrush and bunchgrass, with basin and Wyoming big sagebrush, Thurber needlegrass, Indian ricegrass, bitterbrush, bluegrass, and cheatgrass. Saline areas feature fourwing saltbush, shadscale, and
winter fat. The region is cool enough to have some regeneration capacity and still contains native plants, unlike the Mountain Home Uplands to the west. By far the largest of the Snake River Plain subregions, it covers in southern Idaho, including part of the Craters of the Moon National Monument and Idaho National Engineering Laboratory.
Mountain Home Uplands (12h) The
Mountain Home Uplands ecoregion consists of arid, shrub- and grass-covered plains with hills and basalt-capped
buttes. Elevation varies from 2,500 to 4,300 ft (762 to 1,311 m), with some buttes up to . It is mostly rangeland and is sparsely populated, unlike regions to the west and east. It is flanked by foothills to the north and south and by the Magic and Treasure Valleys to the east and west. Today, it supports cheatgrass,
crested wheatgrass, medusahead wildrye, Wyoming and basin big sagebrush, alkali sagebrush, and
antelope bitterbrush. Stock carrying capacity is low. Native grasses are much rarer and vegetative regeneration capacity is more limited than in the cooler Eastern Snake River Basalt Plains, which has more available moisture. The second largest of the Snake River Plain subregions, it covers in southern Idaho, along the
I-84 corridor between Boise and
Gooding.
Magic Valley (12i) The
Magic Valley ecoregion, named for the irrigation canals of the
Magic Valley that "magically" transformed the region in the early 1900s, is an agricultural valley underlain by alluvium, loess, and basalt flows. Elevation varies from 3,200 to 4,500 ft (975 to 1,372 m). The aridic soils require irrigation to grow commercial crops. Many canals, reservoirs, and diversions supply water to the region's pastureland, cropland, and residential, commercial, and industrial developments. Small grains, alfalfa, sugar beets, potatoes, and beans are grown. Livestock and dairy farms occur; dairying is more common than in the Treasure Valley. Dams, irrigation diversions, pollution, and channel alteration have affected water quality, and over-watering from sprinkler-irrigated portions of the Eastern Snake River Basalt Plains has raised
groundwater levels and created artificial
wetlands. Natural vegetation is mostly sagebrush and bunchgrass, but low terraces have salt tolerant plants. Wyoming and basin big sagebrush, alkali sagebrush, bluebunch wheatgrass, Thurber needlegrass, squirreltail, bluegrass, needle-and-thread, Indian ricegrass, and fourwing saltbush are present.
Population density is greater than in the rangeland-dominated regions to the east and west. The region covers in the
Twin Falls area of southern Idaho.
Unwooded Alkaline Foothills (12j) The
Unwooded Alkaline Foothills ecoregion contains rolling foothills, hills, benches, alluvial fans, and scattered
badlands that are characteristically underlain by sandy,
alkaline lacustrine deposits. Perennial streams are rare. At an elevation of 2,100 to 2,600 ft (671 to 1,189 m), the terrain is higher and more rugged than the neighboring Treasure Valley. The region is valuable as rangeland and wildlife habitat, and land use is generally distinct from the irrigated agriculture of the valley. However, scattered areas near rivers with enough water to leach salts from the soil support alfalfa or sugar beet farming. Natural vegetation is dominated by Wyoming big sagebrush and associated grasses, such as bluebunch wheatgrass, Sandberg bluegrass, Thurber needlegrass, and Indian ricegrass. Today, cheatgrass and crested wheatgrass are also common. Salt tolerant shrubs, including
black greasewood, fourwing saltbush,
inland saltgrass, shadscale,
seepweed, occur on alkaline outcrops. The region covers in western Idaho and in eastern Oregon, on both sides of the Treasure Valley. ==See also==