M333Cc Mission/Swan Valley and Mountains

Landscape Characteristics:

Large intermontane valley with adjacent block faulted mountains that formed in valley fill, till, and metasedimentary rock. Volcanic ash influences most soils. Alpine glaciation has strongly shaped the landscape. Elevations range from 2900 to 9300 feet. Drainage density is moderate. Wetlands and lakes occur frequently in this subsection.

Climate:

Mean annual precipitation ranges from 20 to 110inches, about 80 percent falling as snow in the mountains. The soil temperature and moisture regimes are cryic and udic.

Potential Vegetation:

Douglas-fir forest and Western spruce-fir forest

Relationships of Dominant Map Unit Components:

Landform Geology Soil Taxa
Valley Alluvium/outwash/lacustrine sediments Eutrochrepts/Cryoboralfs/Udifluvents
Mountainsides Till/volcanic ash Cryoboralfs/Eutroboralfs
Alpine ridges/cirquelands argillite/siltite/dolomite/till Cryochrepts

Disturbance and Land Use:

The primary natural disturbances are fire, insects, and windthrow. Land use is predominantly rural and suburban development and some timber harvest.