The Subalpine Ecosystem occupies elevations approximately between 9,000 and 11,000 feet. A typical subalpine forest may consist mostly of subalpine fir and Engelmann spruce. However, previously-burned areas may contain varying amounts, or even almost pure stands, of lodgepole pine. Lodgepole seedlings do well in sunlight, often abundant after fire, but once the forest is established, plant succession may result in increasing amounts of spruce and subalpine fir. Ground cover in a previously-burned forest area often includes two species of huckleberry. Limber pine, with flexible twigs and needles in groups of five, may also be a part of subalpine forests. In high, windblown areas, limber pines often grow into grotesque shapes. Engelmann spruce and subalpine fir, which grow straight and tall in the lower subalpine forests, become shorter and deformed nearer treeline. Even as the trunk grows upward, strong, cold, dry winds may destroy new growth on the windward side, leaving permanent growth only on the lee side of the trunk. Trees with branches on only one side are often called banner trees or flag trees.
At treeline, tree seedlings may germinate on the lee side of rocks and grow only as high as the rock provides wind protection. Further growth is more horizontal than vertical, and additional rooting may occur where branches contact the soil. The resulting low growth of dense trees is called krummholz. Snow cover may protect krummholz trees during the winter, but branches higher than wind-shelters or snow cover are usually destroyed. Well-established krummholz trees may be several hundred to a thousand years old.
Plants and Animals of the Subalpine Ecosystem
Did You Know?
Temperature causes tree line. Trees need an average growing temperature of about 50 degrees fahrenheit.