The Tundra BiomeThe Arctic TundraWe find the arctic tundra biome at high latitudes closely associated with the tundra climate. Notable areas of arctic tundra are found along the arctic coastal North America, Europe, Asia and Greenland. Short grasses, flowers, and grass-like sedges, along with covers of mosses and lichens are the dominate forms of vegetation in the tundra. Seasonal frost heave disrupts root systems preventing support for tall vegetation. The arctic tundra looks like a treeless plain, interrupted by patterned ground and an occasional tree in selected microenvironments.
Pattern ground shown in figure BE.45 is typical of the tundra landscape. Stone polygons, soil circles, stone or soil stripes and terraces are common to both arctic and alpine tundra. These features are created by thrusting action of repeated freezing and thawing of moist soil over a solid substrate like rock or permanently frozen ground. Polygonal patterns dominate flat surfaces. Vegetation is usually confined to the stable parts of the patterns.
Figure BE.46 Tilted poles
on Northway access road, Yukon region Alaska. Permafrost is a common feature of the arctic tundra climate and biome. Permafrost refers to permanently frozen ground. Actually, the ground has two layers which freeze. A surface layer, called the active layer, thaws during the short "summer" and often subsides. Beneath the active layer is the inactive layer which stays frozen throughout the year. Permafrost creates a barrier to the root development. Larger trees can grow along better drained river valleys where the depth to permafrost is greater. The annual freezing and thawing disrupts root systems inhibiting the growth of very tall vegetation.
Permafrost creates an engineering nightmare for the construction of
buildings and other structures. You can see in
Figure BE.46 how telephone poles
have been tilted from the heaving of the surface during freezing and thawing.
Much
concern for damage to the environment was raised over the
construction of the
Trans-Alaska Pipeline. The heated oil running though the
pipeline is insulated from the cold permafrost where it runs
underground. In places it zigzags over the surface on stilts that
allow it to expand and contract with the change in weather.
Figure BE.48 Musk Ox of the Alaskan arctic tundra. (Courtesy: U.S. Fish and Wildlife Service) The Musk Oxen is a well-known inhabitant of the arctic tundra. A dense fur coat protects them from the severe climatic conditions in the tundra. Beneath is a dense fine undercoat that is fairly waterproof. Adults gather in a protective wall to keep the calves safe from predator attacks and severe storms. Musk oxen inhabited much of Eurasia and North America during the Ice Ages, but now survive only in parts of Greenland and northern Canada. Figure BE.49 Arctic National Wildlife
Refuge
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Figure
BE.45 View
of the Alaskan Tundra. (Courtesy: T. Detwyler)*
