A Common Resource Area (CRA) is defined as a geographical area where resource concerns, problems, or treatment needs are similar. It is considered a subdivision of an existing Major Land Resource Area (MLRA) map delineation or polygon. Landscape conditions, soil, climate, human considerations, and other natural resource information are used to determine the geographic boundaries of a CRA.
There are nine CRAs within Nez Perce County (Figure CR.)
Figure CR. Nez Perce County Common Resource Areas. Click on image to view larger version.
Common Resource Area Descriptions
43A.1 Northern Rocky Mountains Grassy Potlatch Ridges
The Grassy Potlatch Ridges ecoregion is underlain by volcanics and mantled by loess and volcanic ash. Idaho fescue, bluebunch wheatgrass, bluegrass, snowberry, and, on cooler, moister sites, scattered ponderosa pine occur and contrast with the forests of the Northern Idaho Hills and the forests and savannas of the Lower Clearwater Canyons. Today, small grain farming, hay operations, and livestock grazing are extensive.
43A.3 Northern Rocky Mountains Lower Clearwater Canyons
The deep, narrow Lower Clearwater Canyons are lower, drier, warmer, and have been more developed than the Lochsa, Selway, and Clearwater Canyons. Savanna, Douglas fir ponderosa pine forest, and, in riparian areas, western red cedar, western white pine, grand fir forest occur. Forests are more widespread on canyon bottoms than on slopes.
43A.8 Northern Rocky Mountains Northern Idaho Hills and Low Relief MountainsThe Northern Idaho Hills and Low Relief Mountains ecoregion is mantled by volcanic ash and loess and has rich, foresttype soils that are unlike the grasslandtype soils of the Columbia Plateau. Grand fir, western red cedar, Douglas fir, and ponderosa pine are common. Its productive forests are widely logged; logging is easier and cheaper than in more rugged terrain.
43C.8 Blue and Seven Devils Mountains Blue and Seven Devils Mountains Dissected UplandsThis unit is characterized by deeply dissected forested mountain slopes. Temperature regime is frigid and the moisture regime is xeric. Vegetation is grand fir, Douglasfir and ponderosa pine. The soils on the north facing slopes retain an ash mantle but south facing slopes lack this mantle due to erosion. Below about 4,500 feet elevation, the Douglas fir forest changes abruptly to the grassland of the Warm Canyons and Dissected Uplands CRA.
8.6 Columbia Plateau Lower Snake and Clearwater Canyons
This unit consists of deeply dissected canyons cut through the basalt layers of the Columbia Plateau. It has isolated plateau fragments of the Dissected Loess Uplands CRA. The depth of the canyons, up to 2,000 feet, create drier conditions and Mean annual precipitation decreases to about 10 inches at the bottom of these canyons. Outside of human population centers and transportation corridors, canyons provide wildlife habitat for bighorn sheep and game birds. Grasscovered: grazing, recreation, and wildlife habitat.
9.2 Palouse and Nez Perce Prairies Palouse Hills
This unit is the western foothills of the Northern Rocky Mountains. This unit is characterized by a nonforested, loess covered area with greater than 15 inches of precipitation. The highly productive soil has a higher organic matter and clay content. Original plant cover has been almost entirely supplanted by wheat farms. Water erosion is the major management issue. Perennial streams originate from the mountains to the east. Smaller, loess bottomed streams rise within the CRA and are intermittent. Many of these intermittent streams are plowed and tiled. Extensive farming including small grains, peas, lentils, hay and pastureland.
9.3 Palouse and Nez Perce Prairies Dissected Loess Uplands
This unit is located on the northeastern slopes of the Blue Mountains. It comprises nonforested, rolling loess hills, canyons, and flat plateau remnants isolated by the lower canyons of the Snake River (CRA 8.6). Grasslands without a sagebrush component dominate the lower elevations. Shrubs (rose and snowberry) appear with increasing moisture at higher elevations. Though grazing and farming have eliminated much of the original plant cover, the dissected terrain and thinner soil is not as suited to agriculture as the neighboring Palouse Hills and Deep Loess Foothills CRAs. Small grain, pea, and hay farming, grazing, and wildlife habitat.
9.11 Palouse and Nez Perce Prairies Nez Perce Prairie
This unit is a loess covered plateau. It is higher, cooler, less hilly, and has shallower soils than the Palouse Hills CRA. Idaho fescue and bluebunch wheatgrass are native. Cropland is now extensive and grows wheat, barley, peas, and hay. The headwaters of many perennial streams are impacted by agricultural land use, negatively impacting the water quality of downstream canyon reaches.