My Research ( Tundra )

The arctic is known for its cold, desert-like conditions. The tundra is the world's coldest and driest biomes. About 1/5 of the Earth is tundra. The word comes from a Finnish word and means 'treeless plain'. 

The main seasons in tundra are winter and summer. Spring and fall are only short periods between winter and summer. Winters in Tundra are very cold and long while summers last for a very short time. The average annual temperature is -18° F (-28° C). Nights can last for weeks when the sun barely rises during some months in the winter, and the temperature can drop to -94° F (-70° C). During the summer the sun shines almost 24 hours a day, which is why the Arctic is also called the Land of the Midnight Sun. Summer are usually warm. Temperatures can get up to 54° F (12° C), but it can get as cold as 37° F (3° C). Average summer temperatures range from 37° to 60°F (3° to 16°C). 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. About a metre under the top layer of soil there is ground that is permanently frozen, called permafrost. In the very short summers, the top level of soil thaws just long enough for plants to grow and reproduce, then become dormant (hibernate) over winter. Since it can't sink into the ground, water from melting permafrost and snow forms lakes and marshes each summer. But the permafrost layer never thaws. Because of this, tundra plants do not have deep root systems. When water soaks the upper soil surface, bogs and ponds may form and provide moisture for plants and small life forms. The Arctic tundra is also a windy place and winds can blow between 30 to 60 miles (48 to 97 kilometers) per hour. Of the North American, Scandinavian and Russian tundras, the Scandinavian tundra is the warmest, with winter temperatures averaging 18°F (-8°C). There is arctic tundra and alpine tundra

Alpine tundra is found on mountain tops all over the world, at the high altitudes where trees cannot grow. The growing season is approximately 180 days. Night temperatures are below freezing. The soil in the alpine tundra is well drained so bogs and ponds do not form. The plants are similar to those in the arctic tundra and include tussock grasses, dwarf trees and small-leafed shrubs.

Access to "the land above the trees" is the single most distinctive aspect of Rocky Mountain National Park. Trail Ridge Road, the highest in any national park, transports you easily to this realm of open sky, tiny but brilliant flowers, and harsh climate. Approximately one-third of this national park is above the limit where trees may grow in northern Colorado.

The Alpine Ecosystem starting at elevations from 11,000 to 11,500 feet, depending on exposure, is an area of extremes. Strong, frequent winds and cold temperatures help limit what plants can grow there. Most alpine plants are perennials. Many plants are dwarfed, but their few blossoms may be full-sized. Cushion plants, looking like ground-hugging clumps of moss, escape the strong winds blowing a few inches above them. Cushion plants may also have long taproots extending deep into the rocky soil. Many flowering plants of the tundra have dense hairs on stems and leaves to provide wind protection or red-colored pigments capable of converting the sun's light rays into heat. Some plants take two or more years to form flower buds, which survive the winter below the surface and then open and produce fruit with seeds in the few weeks of summer.

 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, 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.

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.

The tundra is not a cold and useless wasteland. It is a very fragile environment and the plants and animals that have made their home on the tundra biome have made some incredible adaptations to the long, cold winters and the short but abundant summers. They live on a precarious edge and the smallest stresses can bring about their destruction.

Morphological adaptations such as

     §  large, compact bodies following Bergmann’s and Allen’s rules

     §  a thick insulating cover of feathers or fur

     §  pelage and plumage that turns white in winter, brown in summer

Physiological adaptations such as ability to accumulate thick deposits of fat during the short growing season. Fat acts as insulation and as a store of energy for use during the winter, when animal species remain active.

Population adaptations such as cyclical fluctuations in population size, best seen perhaps in the lemming, a small rodent which is the major herbivore in the tundra’s simple food chain. Predator populations and plant populations respond in kind to the peaks and crashes of the herbivore populations.

Migratory species such as waterfowl, shorebirds and caribou adapt to the tundra by avoiding the most severe conditions of winter. Each year at the end of the short growing season they move southward into the boreal forest or beyond, but return to the tundra to breed.

Aperiodic emigration from the tundra is exhibited by the snowy owl during those years that the lemming populations have crashed. Those winters see snowy owl irruptions as far south as Virginia. Most owls are found with empty stomachs and do not survive to return to the Arctic.

Distribution: The tundra biome is restricted to the high latitudes of the northern hemisphere in a belt around the Arctic Ocean. Many of its species, both plant and animal, have circumpolar distribution areas.

Within the tundra biome a latitudinal zonation of communities is realized:

High Arctic Tundra: essentially confined to the islands of the Arctic Ocean and characterized by scattered lichens and mosses on care rock surfaces and perennial forbs growing in protected crannies among sharp, ice-fractured rock debris.

Middle Arctic Tundra: restricted to the Arctic Coastal plain where level terrain, a thin active layer, and freeze and thaw result in patterned ground, or rock polygons. The sorting of particles by freeze-thaw activity results in a waterlogged center to the polygons, a microhabitat conducive to sphagnum moss and sedges; and an outer ring that is drier and provides a microhabitat favorable to forbs and some dwarf heaths.

Low Arctic Tundra: the majority of the tundra lies on better drained slopes with 

greater depth to permafrost than is encountered on the Arctic coastal plain. Here there is a greater frequency of woody shrubs: willow, birch, and various berry-bearing members of the heath family. Along streams willows and alders may be 10 feet high. On south-facing slopes needleleaf evergreen trees (spruce and fir) are established and represent the northernmost extensions of the great boreal forest to the south. (Such areas where two biomes interdigitate are known as ecotones.)