The forested mountains of the western United States, though primarily thought of as timber resources, provides a large portion of the grazing resource of the west. The higher altitude results in increased precipitation and precipitation effectiveness. Canopy cover of the trees determines the amount of grazing that can occur. The area is mountainous with high mesas and small valleys and elevations of 1500 to 4270 meters. More than 95% of the area is nontillable and can be used only for grazing, timber production, mining, recreation and watershed purposes. This is the area of highest water yield for irrigation, power, and municipal water supplies in the west.

Climate. Precipitation ranges from 38 to over 100 cm annually, and much of it falls during the winter in the form of snow. Growing and grazing seasons vary with latitude and altitude. An altitude of 2500 meters in New Mexico and Arizona will have about 100 days frost free, while in Montana frost is likely to occur at any time at that altitude. In northern regions, the short growing season is partially compensated for by its longer days. The grazing season averages about 3 to 4 months in the northern part of this region and 7 to 8 months in the southern part.

Soils. There is no clearcut soil order for each area. Mollisols, entisols, inceptisols, alfisols, and ultisols occur throughout the region.

Vegetation. The area is about two-thirds timbered or potentially valuable for the production of timber. The different growing and grazing conditions are quite distinctly marked by the different species of timber which occur in belts at various altitudes (Fig. 2). In each belt, the upper edge is limited by temperature (i.e., cold) and the lower limit by the lack of moisture (i.e., it becomes too dry for the association, so it gives way to the more drought resistant type below).

Figure 2. Changes in western mountain plant communities with changes in altitude.

Montane Forest

The montane forest is the most extensive of western forests, ranging from the Black Hills of South Dakota to California, throughout the Rockies, Sierras, and Coast Range, as well as in the mountains of the Great Basin. It extends from Canada to Mexico with a vertical altitudinal range of 900 meters or more. Rainfall in the montane forest ranges from about 50 cm in Colorado and Arizona to 125 to 150 cm on the Pacific Coast. With this added moisture, larger trees are produced along the coast than in the Rockies. In the Rockies, precipitation occurs mostly as winter snow. The montane forest can be divided into two distinct types, the Ponderosa pine and Douglas-fir ecosystem.

Ponderosa Pine.

This vegetation type is the largest of the western mountain forest ecosystem. Due to its open nature it provides a tremendous grazing resource. The ponderosa pine type is found in all the mountain states from Nebraska to the Pacific Coast and from Arizona to Canada.

Climate. The northern areas have a frost free period of 120 days, while in the south it can be 240 days. Annual precipitation ranges from 40 to 75 cm, most coming as snow.

Vegetation. The timber component of the area is largely ponderosa pine (Pinus ponderosa) or sometimes similar species such as Jeffrey pine (P. jeffreyi), sugar pine (P. lambertiana), or limber pine (P. flexilis). Forage species include blue grama, fescues, muhlys (Muhlenbergia), oatgrasses (Danthonia) and bluegrasses. Numerous forbs also provide a significant grazing resource.

Management. Cattle and sheep routinely graze the Ponderosa Pine type. The forests have an average grazing capacity of about 2.4 hectares per animal-unit-month for domestic stock, but that varies greatly with density of tree cover. Both production and utilization are reduced greatly by increased tree overstory. Cattle and elk graze more in openings, but deer use forest and open areas about equally, as do sheep which are herded. Total grazeable area has declined during the past half-century, primarily due to exclusion of fire, which maintains large meadows and keeps the forest floor clean of detritus and shrubby species.

Douglas-fir.

The Douglas-fir ecosystem, though scattered throughout the western mountain region, is most abundant in the Northern Rocky Mountains.

Climate. The climate in the central Rocky Mountains is similar to that of the Ponderosa pine ecosystem, but is moderately wetter. The annual precipitation in that area ranges from 50 to 75 centimeters with a frost-free period of 80 to 120 days. Coastal areas of Washington and Oregon are much wetter with an annual precipitation of 100 to 200 centimeters. Most of the precipitation falls in the winter months. The frost-free period may be as long as 200 days on the coast and 160 days in other parts of Washington and Oregon.

Vegetation. The timber species is primarily Douglas-fir with aspen (Populus tremuloides) and lodgepole pine (Pinus contorta) important cohabitants. Understory vegetation varies with canopy cover. On less favorable sites for tree growth, the open stand provides substantial grazing from fescues, bromes, wheatgrasses, and numerous forbs.

Management. Since the Douglas-fir ecosystem is more mesic than the ponderosa pine ecosystem, less grazing from understory vegetation is available. Most of the grazing occurs in open areas by both cattle and sheep during the summer months. As with the ponderosa pine ecosystem, the open areas have declined due to fire suppression in the area.

Subalpine Forest.

Spruce-fir

The spruce-fir ecosystem is the highest forest zone in the western mountains and occurs throughout. Elevation is as low as 450 meters in the north and 3600 meters in the south.

Climate. Even though precipitation amounts are similar to that of other forest types, evaporation is lower due to increased elevation. Frost may occur at any time of the year over most of the area, but the grazing season varies from 60 to 90 days.

Vegetation. Timber species vary with latitude. Engelmann spruce (Picea engelmanni) and alpine fir (Abies lasiocarpa) are the principal dominants, blue spruce (P. pungens), other firs and western white pine (Pinus monticola) are also important tree species. Openings in the forest have fescues, bluegrasses, needlegrasses, and numerous forbs and woody species.

Management. This forest is dense and dark, with poor undergrowth. Hence it is not of great value for grazing, except in open areas. These openings are used by deer, elk and cattle. The forest tends to be dense and herbaceous plants are scarce beneath dense forest stands. Grassy openings occur in sizes from very small (1 hectare or less) to nearly 40 hectares. Some are natural, others clear-cut. Deer, especially, use the borders of these, elk tend to also, but cattle seem to prefer the openings. Cattle preferred natural openings, elk and deer the created ones. Openings greater than 8 hectares were used little by deer and elk except near forest borders; openings of all sizes were used by cattle. Maintenance and further creation of small openings should improve the deer and elk habitat.