Section M333D Bitterroot Mountains
Geomorphology. This area comprises steep dissected mountains, some with sharp crests and narrow valleys. Elevation ranges from 1,200 to 7,000 ft (366 to 2,135 m). This Section is within the Northern Rocky Mountains physiographic province.
Lithology and Stratigraphy. Predominant rocks are Precambrian metasedimentary of the Belt supergroup.
Soil Taxa. There are frigid and cryic Ochrepts and Boralfs, with some Udands and Cryands on areas where significant amounts of volcanic ash have been deposited. In general, many of the soils have been strongly influenced by deposits of volcanic ash which have made them productive. These soils are generally shallow to moderately deep with loamy to sandy textures.
Potential Natural Vegetation. Kuchler classified potential vegetation as cedar-hemlock-pine forest, Douglas-fir forest, and western ponderosa forest. Common species include western redcedar, western hemlock, western white pine, Douglas-fir, and ponderosa pine. Other important tree species include grand fir and mountain hemlock.
Fauna. Birds are typical of the northern Rocky Mountains, such as Steller's jay and pine siskin. Dabbling ducks, common goldeneye, and harlequin ducks also occur. Other species are flammulated owl, boreal owl in the higher elevations, Lewis' woodpecker, American dipper, pygmy nuthatch, Townsend's solitaire, and yellow-rumped, Nashville, and Townsend's warblers. White-headed woodpeckers reach the edge of their range in this Section. Typical herbivores and carnivores include white-tailed deer, mule deer, elk, moose, black bear, marten, bobcat, and cougar. The woodland caribou historically reached the southern extent of its range within this Section, but is now absent. Smaller common herbivores include the snowshoe hare and the northern flying squirrel. Rare mammals include the gray wolf, fisher, wolverine, northern bog lemming, and Coeur d' Alene salamander. Typical Herpetofauna are the spotted frog, Pacific treefrog, western toad, long-toed salamander, and possibly the Pacific giant salamander.
Climate. Precipitation averages 40 to 80 in (1,020 to 2,030 mm); most precipitation in fall, winter, and spring is snow; summers are relatively dry. Temperature averages 36 to 45 F (2 to 7 C). Climate is maritime-influenced, cool, moist temperate with relatively mild winters and dry summers. The growing season ranges from 45 to 100 days.
Surface Water Characteristics. Perennial streams are generally fairly steep and deeply incised, exhibiting much structural control. Major rivers include the Clark Fork and the North Fork of the Clearwater.
Disturbance Regimes. Fire, insects, and disease are the principal natural sources of disturbance. Mass wasting also occurs in some areas. Fires were mostly large, low frequency, high intensity, stand-replacing fires, except for the eastern quarter of the Section, which had mostly low intensity, frequent ground fires. Fire suppression efforts have altered the fire regime to a large extent.
Land Use. Timber harvest, wildlife habitat, and recreation are dominant land uses. Some grazing and mining also occur.
