[2] As defined by the EPA, ecoregions are, "Areas of similarity regarding patterns in the mosaic of abiotic and biotic, aquatic and terrestrial ecosystem components, including geology, physiography, vegetation, climate, soils, hydrology, land use, and wildlife, with humans being considered as part of the biota.
Realms characterize large amounts of habitat that contain organisms that have been evolving together in relative isolation for long time periods.
A batholith is a body of intrusive igneous rock formed by the cooling of magma under the Earth's surface.
[11][12] Soils derived from the granite that characteristically underlays the ecoregion tend to retain water poorly and be limited in fertility.
[13] The rivers that flow through the ecoregion include the Payette, Selway, Salmon, Lochsa, Clearwater, Boise in Idaho, and the Bitterroot in Montana.
[14][15] The region lies within the Columbia and Missouri Watersheds for named rivers as designated by the United States Geological Survey (USGS).
Its surface waters tend to be very low in alkalinity, which is caused by its underlain intrusive rocks of the Cretaceous Idaho Batholith.
Granitic rocks underlay the region which is spread out by volcanic ash deposits that help improve the soil fertility and water retention in the uplands.
Engelmann spruce (Picea engelmannii) and subalpine fir grow at high elevations, while cedar-hemlock-pine forests are found in canyons and on north-facing slopes.
Unlike any other parts of the Idaho Batholith ecoregion, there is a mosaic of shrubland, open Douglas-fir forests, and aspen occurs.
Mining is affecting water quality, and rapid residential and commercial growths are occurring near the city of Ketchum, Idaho.
[20] The Glaciated Bitterroot Mountains and Canyons ecoregion is spread out by volcanic ash and sediment left from glaciers.
The summits of mountains are high enough here to capture moisture from the Pacific Ocean, unlike in nearby ecoregions.
Part of the region is situated near Boise, Idaho, which is experiencing residential development in rural areas; otherwise, land is mostly used for grazing.
[24] Annual precipitation is greater than surrounding ecoregions at lower elevations and the mountains are often capped with snow.
[20] Soils derived from granitic rocks, which are characteristically poor at retaining water spread out the Southern Forested Mountains ecoregion.
Like much of the Idaho Batholith ecoregion, soil disturbance results in high amounts of sediment being deposited in streams.
[25][26] According to the National Oceanic and Atmospheric Administration (NOAA), the ecoregion received anywhere from 10-80 inches (25.4-203.2 cm) of precipitation for the entire 2012 calendar year.
Thunderstorms have a large impact on the amounts of precipitation in the region and greatly influence flood events and erosion.
[30] The resources in the ecoregion include fishing, crop production, grazing, mining, logging, and recreation.
Slide failures, which produce debris flows, and floods with increased amounts of sediment are some of the known results of prolonged storms in the region.
Fires help speed up the removal of vegetation from the soil, which in turn increases the rate of erosion and sediment transport.
[29] Resource extraction in the region includes but is not limited to logging, fishing, mining, and removal of vegetation via livestock grazing.
[20] Due to the mountainous terrain of the region, much of the land within the Idaho Batholith is inaccessible to automobiles, thus in a more natural state.