Saturday, May 14, 2011

Tundra Biome


        In the very cold places of the world, survival isn't easy. The soil is frozen, its top surface thawing only during summer, and no trees can grow. Yet plants and animals that are adapted for the harsh conditions thrive. This biome is called tundra. Most of the world's tundra is found in the north polar region. It is called Arctic tundra. There is a small amount of tundra on parts of Antarctica that are not covered with ice. Plus, tundra is found on high altitude mountains and is called alpine tundra.
       
          Permafrost is the term given to frozen soil. During the winter months, permafrost reaches the surface of the tundra. It is very cold during the winter, with temperatures reaching -60 degrees Fahrenheit (-51 degrees Celsius). Very few animals are active in these harsh conditions.

          In the summer time, the tundra changes. The Sun is out almost 24 hours a day, so the tundra starts to warm up. The permafrost melts at the surface, and plant life grows. However, the permafrost only disappears for a few inches below the surface. There isn't enough soil for trees to grow, so only small plants are found in the tundra.

            At the same time, a variety of animals come out to feast on the plants. Insects come to feed on the animals, and birds appear to enjoy the insects.
Characteristics of tundra include:
  1. Extremely cold climate
  2. Low biotic diversity
  3. Simple vegetation structure
  4. Limitation of drainage
  5. Short season of growth and reproduction
  6. Energy and nutrients in the form of dead organic material
  7. Large population oscillations
Tundra is separated into two types:

Arctic tundra

                  Arctic tundra is located in the northern hemisphere, encircling the north pole and extending south to the coniferous forests 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 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. 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 1,700 kinds of plants in the arctic and subarctic, and these include:
  • low shrubs, sedges, reindeer mosses, liverworts, and grasses
  • 400 varieties of flowers
  • 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:
  • Herbivorous mammals: lemmings, voles, caribou
  • Carnivorous mammals: arctic foxes, wolves, and polar bears
  • Migratory birds: ravens, snow buntings, falcons, loons,
  • Insects: mosquitoes, flies, moths, grasshoppers
  • Fish: 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

     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. 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: pikas,, mountain goats, sheep
  • Birds: grouselike birds
  • Insects: springtails, grasshoppers ,beetles