Plant succession in the Rocky Mountain Trench: Influence of historical factors

Abstract

There are approximately 250,000 ha of land in the Ponderosa Pine and Interior Douglas-fir biogeoclimatic zones in the Rocky Mountain Trench and adjointing side-valleys between the U.S. border and Golden, British Columbia (BC). Under climax conditions, the Ponderosa Pine Zone is dominated by ponderosa pine with an understory of rough fescue, Idaho fescue, bluebunch wheatgrass and a variety of forbs and shrubs. In the drier parts of the Interior Douglas-fir Zone, Douglas-fir is the principal tree with an understory of bluebunch wheatgrass, rough fescue, and Richardson's needlegrass combined with forbs such as western yarrow and timber milkvetch. In wetter parts of the zone, pinegrass is the dominant grass at higher stages of succession. These dry forests provide habitat and forage for whitetail deer, mule deer, elk, and cattle. Numerous sources of disturbance have modified both these forest types historically, which have had significant effects on plant communities and the forage resource in the Rocky Mountain Trench.