The tundra biome is the coldest of all the biomes. Tundra comes from the Finnish word tunturi, meaning treeless plain. It is noted for its frost-molded landscapes, extremely low temperatures, little precipitation, poor nutrients, and short growing seasons. Dead organic material functions as a nutrient pool. The two major nutrients are nitrogen and phosphorus. Nitrogen is created by biological fixation, and phosphorus is created by precipitation.
Arctic tundra is located in the northern hemisphere, encircling the north pole and extending south to the coniferous forests (Forest biome) of the taiga. The arctic is known for its cold, desert-like conditions. The growing season ranges from 50 to 60 days. The average winter temperature is -34° C (-30° F), but the average summer temperature is 3-12° C (37-54° F) which enables this biome to sustain life. Rainfall may vary in different regions of the arctic. Yearly precipitation, including melting snow, is 15 to 25 centimeters (cm) (6 to 10 inches). Soil is formed slowly. A layer of permanently frozen subsoil called permafrost exists, consisting mostly of gravel and finer material. When water saturates the upper surface, bogs and ponds may form, providing moisture for plants.
Flora and Fauna
There are no deep root systems in the vegetation of the arctic tundra, however, there are still a wide variety of plants that are able to resist the cold climate. There are about 1700 kinds of plants in the arctic and subarctic, and these include: low shrubs, sedges, reindeer mosses, liverworts, and grasses, 400 varieties of flowering plants, crustose and foliose lichen.
All of the plants are adapted to sweeping winds and disturbances of the soil. Plants are short and group together to resist the cold temperatures and are protected by the snow during the winter. They can carry out photosynthesis at low temperatures and low light intensities. The growing seasons are short and most plants reproduce by budding and division rather than sexually by flowering.
The fauna in the arctic is also diverse (Species diversity). Herbivorous mammals include lemmings, voles, caribou, arctic hares and squirrels. Carnivorous mammals include arctic foxes, wolves, and polar bears. Migratory birds include ravens, snow buntings, falcons, loons, ravens, sandpipers, terns, snow birds, and various species of gulls. Insects include mosquitoes, flies, moths, grasshoppers, blackflies and arctic bumble bees. Artic fishes include cod, flatfish, salmon, and trout.
Animals are adapted to handle long, cold winters and to breed and raise young quickly in the summer. Animals such as mammals and birds also have additional insulation from fat. Many animals hibernate during the winter because food is not abundant. Another alternative is to migrate south in the winter, like birds do. Reptiles and amphibians are few or absent because of the extremely cold temperatures. Because of constant immigration and emigration, the population continually oscillates.
Alpine tundra is located on mountains throughout the world at high altitude where trees cannot grow. The growing season is approximately 180 days. The nighttime temperature is usually below freezing. Unlike the arctic tundra, the soil in the alpine is well drained.
Flora and Fauna
The plants are very similar to those of the arctic ones and include tussock grasses, dwarf trees, small-leafed shrubs, and heaths. Animals living in the alpine tundra are also well adapted. Mammals inlcude pikas, marmots, mountain goats, sheep, and elk. Birds include grouselike birds. Insects include springtails, beetles, grasshoppers, butterflies.
- Tundra Biome, UCMP.
- Tundra Biome, NASA Earth Observatory.
- University of California Museum of Paleontology Homepage