Vegetational pattern near alpine timberline as affected by fire-snowdrift interactions

Abstract

In the central Rocky Mountains, flat areas or gentle slopes just below climatic timberline exhibit a vegetational pattern consisting of ribbon forests and snow glades lying across the path of the prevailing winds. The pattern is the result of removal of snow by wind from the open areas and its deposit in a great drift about 60 to 100 m in from the windward edge of the forest. This drift remains too long during the summer for tree growth. Consequently, the vegetation in the drift area is a wet or moist subalpine meadow occupying the snow glade and, in effect, breaking the forest into ribbon-like patches. The source area for the snow may be natural climax tundra, tundra which has replaced burned subalpine forest, or subalpine meadow of edaphic origin. The ribbon-forest and snow-glade pattern can be expected just below climatic timberline wherever plateaus or gentle slopes are exposed to heavy snowfall, strong winter winds, and cool summers. Destruction of such ribbon forests by fire or cutting will result in new snowdrift patterns and the long-lasting replacement of the forest by alpine or subalpine meadow vegetation.