Tundra

Tundra is the global biome that consists of the treeless regions in the north (Arctic tundra) and high mountains (alpine tundra). The vegetation of tun­dra is low growing, and consists mainly of sedges, grasses, dwarf shrubs, wildflowers, mosses, and lichens. The word “tundra” is derived from the Finnish word “tunturi,” which refers to the upland treeless parts of hills and low mountains free of woodlands.

Tundra climates are extremely cold and snowy in winter. Summers are cool. The southern or lower limit of trees corresponds roughly to a mean July temperature between 10 and 12 degrees Celsius (50 and 53.6 degrees Fahrenheit), but in maritime areas the limiting summer temperature can be lower. Low shrubs, less than about 1 meter (3.2 feet) tall, and peaty soils are common near treeline. In the northern extremes and at higher elevations, the landscapes are predominantly barren with scattered wild- flowers, such as purple mountain saxifrage and Arctic poppies, mosses, and lichens. Most of the Arctic tundra regions are underlain by permafrost, ground that is permanently frozen beneath a shallow layer of soil that thaws annually.

Tundra ecosystems have a variety of animal species that do not exist in other regions, including the Arctic hare, musk oxen, lemmings, Arctic ground squirrels, and ptarmigan. Other animals migrate annually to the Arc­tic including caribou and many species of birds.

The Arctic tundra is the least exploited of Earth’s biomes. It is a unique biological laboratory for scientists to study unaltered ecosystems. The chief ecological concerns in the Arctic tundra are cumulative impacts of oil and mineral exploitation, roads, tourism, and long-range transport of air pollu­tion from industrial centers to the south. Global warming is likely to have its greatest effect on tundra. Major concerns are the fate of permafrost and the carbon contained in Arctic peat. Decomposition of this carbon could in­crease the concentration of carbon dioxide in the atmosphere.

References

Wielgolaski, F. E. Polar and Alpine Tundra. The Netherlands: Elsevier, 1997.

مواضيع ذات صلة

Flow cytometry

البروتوبلازم Protoplasm

غشاء الخلية The cell membrane

مملكة البدائيات (Monera)

كيس الصفار ( المح ) Yolk sac

اقسام البيئة البحرية

بيئة المياه البحرية

المياه الجارية

المياه الساكنة

بيئة المياه العذبة

المناطق الاحيائية المائية

السهوب (السفانا) Savanna