Tundra is the coldest of all the biomes. Tundra comes from the
Finnish word tunturia, 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.
Tundra is separated into two types: arctic
tundra and alpine
tundra.
Characteristics of Tundra
- Extremely cold climate
- Low biotic diversity
- Simple vegetation structure
- Limitation of drainage
- Short season of growth and reproduction
- Energy and nutrients in the form of dead organic material
- Large population oscillations
Arctic
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, arctic hares and squirrels
- Carnivorous mammals: arctic foxes, wolves, and polar bears
- Migratory birds: ravens, snow buntings, falcons, loons, ravens,
sandpipers, terns, snow birds, and various species of gulls
- Insects: mosquitoes, flies, moths, grasshoppers, blackflies and arctic
bumble bees
- 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
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, marmots, mountain goats, sheep, elk
- Birds: grouselike birds
- Insects: springtails, beetles, grasshoppers, butterflies
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