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Hikers traversing the Franconia Ridge in the White Mountains, much of which is in the alpine zone.

Alpine tundra is an ecozone that does not contain trees because it has high altitude. Alpine tundra is distinguished from arctic tundra, because alpine tundra does not have permafrost, and alpine soils are generally better drained than arctic soils. Alpine tundra transitions to subalpine forests below the tree line; stunted forests occurring at the forest-tundra ecotone are known as Krummholz.

Alpine tundra occurs in mountains worldwide. The flora of the alpine tundra is characterized by dawrf shrubs close to the ground. The cold climate of the alpine tundra is caused by the low air pressure, and is similar to polar climate.

Contents

Distribution

Alpine tundra occurs at high enough altitude at any latitude. Portions of Montane grasslands and shrublands ecoregions worldwide include alpine tundra. Large regions of alpine tundra occur in the American Cordillera in North and South America, the Alps and Pyrenees of Europe, the Rift Mountains of Africa, and a large portion of the Tibetan Plateau.[1]

Flora

Flora of an alpine environment

The alpine tundra ecozone 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 alpine 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.[2]

Alpine meadows form where sediments from the weathering of rocks has produced soils well-developed enough to support grasses and sedges. Non-flowering lichens cling to rocks and soil. Their enclosed algal cells can photosynthesize at any temperature above 0 °C (32 °F), and the outer fungal layers can absorb more than their own weight in water. The adaptations for survival of drying winds and cold may make tundra vegetation seem very hardy, but in some respects the tundra is very fragile. Repeated footsteps often destroy tundra plants, leaving exposed soil to blow away, and recovery may take hundreds of years.[2]

Fauna

An alpine mire in the Swiss Alps

Because alpine tundra is located in various widely-separated regions of the Earth, there is no animal species common to all areas of alpine tundra. Some animals of alpine tundra environments include the Kea parrot, marmot, mountain goats, chinchilla, woodland caribou, and pika.

Climate

Summer in Northern Sweden's Tarfala Valley with its alpine climate

Alpine climate is the average weather (climate) for the alpine tundra ecozone. The climate becomes colder at high elevations—this characteristic is described by the lapse rate of air: air tends to get colder as it rises, since it expands. The dry adiabatic lapse rate is 10 °C per km of elevation or altitude. Therefore, moving up 100 meters on a mountain is roughly equivalent to moving 80 kilometers (45 miles or 0.75° of latitude) towards the pole.[3] This relationship is only approximate, however, since local factors such as proximity to oceans can drastically modify the climate.

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Quantifying the climate

This alpine valley is entirely above the tree line

There have been several attempts at quantifying what constitutes an alpine climate.

Climatologist Wladimir Köppen demonstrated a relationship between the Arctic and Antarctic tree lines and the 10 °C summer isotherm; i.e., places where the average temperature in the warmest calendar month of the year is below 10 °C cannot support forests. See Köppen climate classification for more information.

Otto Nordenskiöld theorized that winter conditions also play a role: His formula is W = 9 − 0.1 C, where W is the average temperature in the warmest month and C the average of the coldest month, both in degrees Celsius (this would mean, for example, that if a particular location had an average temperature of −20 °C in its coldest month, the warmest month would need to average 11 °C or higher for trees to be able to survive there).

In 1947, Holdridge improved on these schemes, by defining biotemperature: the mean annual temperature, where all temperatures below 0 °C are treated as 0 °C (because it makes no difference to plant life, being dormant). If the mean biotemperature is between 1.5 °C and 3 °C,[4] Holdridge quantifies the climate as alpine.

See also

References


Simple English

File:Alpine
Alpine tundra.

Alpine tundra is a type of geological terrain. It is to be found at high enough altitude at any latitude on Earth. Alpine tundra lacks trees. The lower parts do not have permafrost. Because of this they are generally better drained than permafrost soils. Alpine tundra changes to subalpine forests below the tree line.

Because alpine tundra is located in many different widely-separated regions of the Earth, there is no animal species found in all areas of alpine tundra.

Some animals of alpine tundra environments include the Kea parrot, marmot, Mountain goats, chinchilla, pika, golden eagle and snow leopard.

Temperatures and Rainfall

Very cold and dry. Winter temperatures below 10ºC. Mainly mosses, lichens and poor grasses. Some dwarf trees like birch and alder grow in Tundras.

Geographic possition of Tundras

Tundras are mainly found in Northern areas such as Siberia and the North of Canada


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