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GLACIER National Park |
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 The Forests of Glacier From the lush redcedar-hemlock forest in the McDonald Valley to the subalpine fir, whitebark pine, and Englemann spruce struggling for existence near treeline, the forests of Glacier reflect the conditions of temperature, exposure, soil, and drainage prevailing; and each forest has its characteristic association of understory trees and shrubs, herbaceous ground cover, and vertebrate and invertebrate animal life. |
 Life Zones Many physical and climatic factors determine the range of Glacier's plant-and-animal communities. Boundaries between communities are seldom sharply defined, but rather merge together in broad zones of transition. With elevation gain, average daily temperature drops at the rate of 5° per 900 meters. Precipitation, wind velocity, and evaporation loss increase. Soil thins. These factors, along with others such as fire frequency, north or south exposure, and availability of moisture, combine to determine the range of each community. In the forest community below 1,800 meters, Douglas-fir, lodgepole pine, and western larch predominate. In the valleys, Engelmann spruce and subalpine fir are found. The somewhat lower and much better watered western valleys of the park support western redcedar and western hemlock. Treeline is the upper limit to which the tolerances of trees to environmental conditions permit them to grow. Because there are so many controlling factors (wind, temperature, exposure to sunlight, snow cover, etc.) treeline in the diagram is only approximate. In Glacier it averages 2,000 meters. Avalanche chutes or sheer cliff walls may suppress it to below 1,500 meters: on protected slopes it may be as high as 2,150 meters. At the eastern edge of the park below 1,200 meters, the forest gives way to the prairie community, composed mostly of soft-stemmed plants adapted to the conditions of low precipitation that prevail here in the rainshadow of the mountain range. Clumps of aspen, found in the prairie in sheltered spots, occur here in the transition zone between prairie and forest. (click on above image for an enlargement in a new window) |
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Last Modified: Sat, Nov 4 2006 10:00:00 pm PST |