Resumo de The Amazing Tundra

Tundra 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.
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 ? Alpine tundra 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 sub arctic, 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,
black flies 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 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: picas, marmots, mountain goats,
sheep, elk ? Birds: grouse like birds There are two types of tundra in the
world, Arctic and Alpine. The arctic tundra is at the top of the world around
the North Pole. The tops of tall cold mountains are alpine tundra. The most
distinctive characteristic of the tundra soil is its permafrost, a permanently
frozen layer of ground often 2000 feet thick. Shallow rooted tundra plants and
microorganisms grow in the permafrost. Animals are adapted to handle cold
winters and to breed and raise young quickly in the short summers. Average
yearly temperatures range from -70 degrees F to 20 degrees F. Artic wildlife is
circumpolar (surrounding or near either pole of the earth), the same or closely
related species are found around the world. The variety of animal life is also
limited in the challenging environment. Musk-ox, caribou, and reindeer are the
dominant large grazers, feeding on grass, sedge, lichen, and willow. Arctic
hare, or snowshoe rabbit, and lemming feed on grass and sedge. Predators
include the wolf, artic fox, and snowy owl. Polar bears, and sometimes brown
bears are seen. Many birds nest in the tundra shrubbery in summer, migrating to
milder climates before the winter season sets in.

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