Tundra Tundra comes from the Finnish word "tunturia", which means a barren land. Tundra is the youngest of all the biomes. It was formed 10,000 years ago. It is located at latitudes 55° to 70° North, the tundra is a vast and treeless land which covers about 20% of the Earth's surface, circumnavigating the North pole. The tundra is freezing for almost all of the year with no traditional seasons, only a very long winter. Winter conditions in the tundra exist most of the year, with the exception of a very short mild season which passes for summer. The tundra is basically like a desert when it comes to precipitation. Only about 6 - 10 inches of precipitation (mostly snow) fall each year. Below the soil is the tundra's permafrost, a permanently frozen layer of earth. During the short summers the top layer of soil may thaw just long enough to let plants grow and reproduce. Since it can't sink into the ground, water from melting permafrost and snow forms lakes and marshes each summer. There is barely any vegetation in the tundra, only about 1,700 different species, which isn't very much. These are mostly shrubs, sedges, mosses, lichens and grasses. There are about 400 varieties of flowers. The growing season is only about 50 to 60 days long. There are no trees, except for some birches in the lower latitudes. The ground is always frozen beneath the top layer of soil, so trees can't send their roots down. Willows do grow on some parts of the tundra but only as low carpets about 3 inches (8 cm) high. Most plants grow in a dense mat of roots which has developed over thousands of years. The soil is very low in nutrients and minerals, except where animal droppings fertilize the soil. The tundra is a very fragile environment. The extremely cold temperatures makes it a difficult environment to survive in during the winters, and plants and animals have a hard time coping with any extra stresses and disturbances. More people moving to the tundra to work in the mines and oil rigs have created towns and more roads. Some animal's movements to traditional feeding and denning grounds have been disrupted by these obstacles. When they try to pass through a town they are often scared away or shot. With their feeding patterns disrupted, many polar bears have starved. The Alaskan oil pipeline was built across a caribou migration route. In some places the pipeline has been raised above the ground so the caribou can pass under it. Pesticides have been used to control the hordes of insects. Thousands of migrating birds come to the tundra because of the abundant insects. Through the food chain the pesticides reach many of the animals that live on the tundra. Pollution from mining and drilling for oil has polluted the air, lakes and rivers. The land around some nickel mines in Russia has become so polluted that the plants in the surrounding area have died. Footprints and tire tracks can be visible for many years after they were made. When the sun hits the ruts it causes the permafrost to melt. This causes erosion and the ruts get bigger, and eventually the ruts turn into gullies. Tracks made during WW II have grown so large that some of them are now lakes. Tundra is very important for the global enviroment. The tundra is one of Earth's three major carbon dioxide sinks. A carbon dioxide sink is a biomass which takes in more carbon dioxide than it releases. Carbon dioxide is a greenhouse gas that contributes to global warming. During the short summer tundra's plants take in carbon dioxide, sunlight and water in the process of photosynthesis. Plants normally give off carbon dioxide after they die and decompose. But because of the short, cool summer and freezing winter temperatures, plants can't decompose. Remains of plants thousands of years old have been found in the tundra permafrost. In this way the tundra traps the carbon dioxide and removes it from the atmosphere. Today global warming is melting the permafrost of the tundra and every year several feet of tundra are lost. As the tundra melts, the plant mass decomposes and returns carbon dioxide to the atmosphere. Tundra can be divided into 2 groups. The arctic tundra and the alpine tundra. Alpine tundra- Alpine tundra occurs in climatically stressed environments at high mountainous altitudes. Alpine tundra can even occur on mountaintops at tropical latitudes, although this vegetation type is much more common in temperate regions. Compared with the arctic tundra, alpine environments have much larger daily variations of temperature and solar radiation during the growing season. Because of the thinness of the atmosphere at high altitude, alpine tundra is also subject to large inputs of ultraviolet radiation, which can be an important biological stressor. Because the skies are often clear at high altitude, the surface cools very quickly at night, so that frost can be a daily occurrence during the growing season. In general, alpine tundra is considerably richer in plant species than arctic tundra. At temperate latitudes, this occurs because alpine environments were not regionally obliterated by glacial ice during the most recent glaciations, so the component species were able to endure this period of intense climatic stress. This survival was made possible by the occurrence of non-glaciated refugia where plants could survive on some mountaintops (these are called nunataks). In addition, as the climate deteriorated, alpine tundra could migrate to lower-altitude, non-glaciated parts of mountainous regions, as the tree-line moved downwards. In contrast, almost all of the arctic tundra was destroyed by the extensive continental glaciers that covered northern regions during the most recent ice ages. It is believed that after deglaciation the arctic tundra was re-established by a northward migration of some of the plant species of alpine tundra. However, because only some species were capable of undertaking the extensive migrations that were necessary, the arctic tundra is relatively poor in species, compared with temperate alpine tundras. There are relatively few animals that only occur in alpine tundra and not in other types of ecosystems. In North America some of the characteristic mammals of alpine tundra include a small relative of rabbits called the pika (Ochotona princeps), and the hoary marmot (Marmota caligata). The gray-crowned rosy finch (Leucostichte tephrocotis), horned lark (Eremophila alpestris), and water pipit (Anthus spinoletta) all breed in alpine tundra of North America, but also in arctic tundra (the lark also breeds in other open habitats, such as prairie and fields). Arcitc tundra – Arctic tundra is found almost entirely in the Northern Hemisphere. In the southern hemisphere it is found on isolated islands off the coast of Antarctica as well as the Antarctic peninsula. The tundra falls between two other major biomes, the taiga and ice caps. In essence the zone is controlled by the extremes in the weather. If its too cold, the ice caps don't melt enough to allow vegetation. If its a bit warmer, trees are able to send roots deep enough to root and grow. In the arctic tundra there are two seasons: winter and summer. In the summer, the sun is present almost 24 hours a day. This sun however, only warms the tundra up to a range of about 3°C to 12°C. In the winter the opposite light conditions are present. There are several weeks where the sun never rises. This causes the temperatures to drop to extremely cold levels. The average temperature of the tundra is around -28°C while extremes can dip to -70°C. Arcitc tundra gets much less precipitation than alpine tundra. It gets only a couple of inches more than a desert. Precipitation levels in the tundra are from 6 to 10 inches a year. Most of this falls as snow. In many ways this biome is a cold desert, lacking significant precipitation. However, something that many people might find unusual given the lack of rain or snow is the presence of a lot of standing water. This is the result of the permafrost. Each summer, the upper layer melts just enough to create small bogs and pools. The water will not soak into the ground however, because the permafrost blocks it. In the winter these pools freeze and the cycle repeats itself. Very little moisture is lost to evaporation. On a relative scale, the arctic tundra biome has a relatively low biodiversity. There are around 1700 species of plants that live in this zone. There are almost no reptiles or amphibians. There are only 48 land mammals that make this habitat their home. However, even though this zone has very few species the number of individuals in each species that make this biome a home for part of the year is very large. Take the massive herds of caribou or flocks of migratory birds as an example. Many animals migrate to the tundra in the summer months to take advantage of the lack of predators, abundant plants, insects, and fish. Snowy Owls breed on the ground in the summer months, and prey on voles, lemmings and other small rodents. Musk oxen, a smaller cousin of the Ox feeds on the grasses in small herds. They defend themselves from one of the few predators, packs of wolves. Sources: http://en.wikipedia.org/wiki/Tundra http://www.thewildclassroom.com/biomes/arctictundra.html http://ths.sps.lane.edu/biomes/tundra3/tundra3.html http://www.blueplanetbiomes.org/tundra.htm