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Spruce-fir forest in the Canadian Rockies. The Rocky Mountains subalpine zone is the biotic zone immediately below tree line in the Rocky Mountains of North America.In northern New Mexico, the subalpine zone occupies elevations approximately from 9,000 to 12,000 feet (2,700 to 3,700 m); [1] while in northern Alberta, the subalpine zone extends from 1,350 to 2,300 metres (4,400 to 7,500 ft).
Because the Sierran subalpine is situated in such harsh conditions, i.e. nearly at the limit of tree growth, the ecosystem is particularly sensitive to changes in climate. The long-lived nature of subalpine species plus their relative isolation from civilization make subalpine ecosystems a particularly good study system to examine climate change.
The elevation where trees fail to grow is called the tree line. The biotemperature of the subalpine zone is between 3 and 6 °C (37 and 43 °F). [5] Above the tree line the ecosystem is called the alpine zone or alpine tundra, dominated by grasses and low-growing shrubs. The biotemperature of the alpine zone is between 1.5 and 3 °C (34.7 and ...
Larix lyallii, the subalpine larch, or simply alpine larch, is a deciduous, coniferous tree native to northwestern North America. It lives at high altitudes, from 1,500 to 2,900 meters (4,900 to 9,500 ft), [3] in the Rocky Mountains of Idaho, Montana, British Columbia, and Alberta. There is a disjunct population in the Cascade Range of Washington.
The upper montane forest is replaced by the subalpine forest near 9,000 feet (2,700 m), where the climate is cooler with an even shorter growing season due to long, cold, and snowy winters. Accumulations of three to nine feet (1 to 2.5 m) of snow are typical. The most common tree in the subalpine forest is the whitebark pine. [10]
There are two or three taxa in subalpine fir, treated very differently by different authors: . The Coast Range subalpine fir (Abies lasiocarpa) [4] in the narrow sense, is the typical form of the species, occurring in the Pacific Coast Ranges, the Olympic Mountains and the Cascade Range from Southeast Alaska (Panhandle mountains) south to California.
Krummholz Pinus albicaulis in Wenatchee National Forest Wind-sculpted krummholz trees, Ona Beach, Oregon. Krummholz (German: krumm, "crooked, bent, twisted" and Holz, "wood") — also called knieholz ("knee timber") — is a type of stunted, deformed vegetation encountered in the subarctic and subalpine tree line landscapes, shaped by continual exposure to fierce, freezing winds.
In the higher boundaries of subalpine ecosystem, where the abiotic conditions are more stressful, trees are clumped together in patchy islands. Trees in this area can be recognized by its krummholz form. Trees of this upper boundary will take on a flag appearance with branches extending from one side indicating the prevailing wind directions.