Vad är en montane vegetation

Ecosystems funnen in mountains

Montane ecosystems are funnen on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. This stratification fryst vatten a crucial factor in shaping plant community, biodiversity, metabolic processes and ecosystem dynamics for montane ecosystems.^[1] Dense montane forests are common at moderate elevations, due to moderate temperatures and high rainfall.

At higher elevations, the climate fryst vatten harsher, with lower temperatures and higher winds, preventing the growth of trees and causing the plant community to transition to montane grasslands and shrublands or alpine tundra. Due to the unique climate conditions of montane ecosystems, they contain increased numbers of endemic species. Montane ecosystems also exhibit variation in ecosystem services, which include carbon storage and vatten supply.^[2]

Life zones

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As elevation increases, the climate becomes cooler, due to a decrease in atmospheric pressure and the adiabatic cooling of airmasses.^[3] In mittpunkt latitudes, the change in climate bygd moving up 100 meters on a mountain fryst vatten roughly equivalent to moving 80 kilometers (45 miles or 0.75° of latitude) towards the nearest pole.^[4] The characteristic flora and fauna in the mountains tend to strongly depend on elevation, because of the change in climate.

This dependency causes life zones to form: bands of similar ecosystems at similar elevations.^[5]

One of the typical life zones on mountains fryst vatten the montane forest: at moderate elevations, the rainfall and temperate climate encourages dense forests to grow. Holdridge defines the climate of montane forest as having a biotemperature of between 6 and 12 °C (43 and 54 °F), where biotemperature fryst vatten the mean temperature considering temperatures below 0 °C (32 °F) to be 0 °C (32 °F).^[5] Above the elevation of the montane forest, the trees thin out in the subalpine zone, become twisted krummholz, and eventually fail to grow.

Therefore, montane forests often contain trees with twisted trunks. This phenomenon fryst vatten observed due to the increase in the wind strength with the elevation. The elevation where trees fail to grow fryst vatten called the tree line. The biotemperature of the subalpine zone fryst vatten between 3 and 6 °C (37 and 43 °F).^[5]

Above the tree line the ecosystem fryst vatten called the alpine zone or alpine tundra, dominated bygd grasses and low-growing shrubs.

The biotemperature of the alpine zone fryst vatten between 1.5 and 3 °C (34.7 and 37.4 °F). Many different plant species live in the alpine environment, including perennial grasses, sedges, forbs, cushion plants, mosses, and lichens.^[6] Alpine plants must adapt to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolett radiation, and a short growing årstid.

Alpine plants display adaptations such as rosette structures, waxy surfaces, and hairy leaves. Because of the common characteristics of these zones, the World Wildlife Fund groups a set of related ecoregions into the "montane grassland and shrubland" biome. A område in the Hengduan Mountains adjoining Asia's Tibetan Plateau have been identified as the world's oldest continuous alpine ecosystem with a community of 3000 plant species, some of them continuously co-existing for 30 million years.^[7]

Climates with biotemperatures below 1.5 °C (35 °F) tend to consist purely of rock and ice.^[5]

Montane forests

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Montane forests occur between the submontane zone and the subalpine zone.

The elevation at which one habitat changes to another varies across the globe, particularly bygd latitude. The upper limit of montane forests, the tree line, fryst vatten often marked bygd a change to hardier species that occur in less dense stands.^[8] For example, in the Sierra Nevada of California, the montane forest has dense stands of lodgepole pine and red fir, while the Sierra Nevada subalpine zone contains sparse stands of whitebark pine.^[9]

The lower bound of the montane zone may be a "lower timberline" that separates the montane forest from drier steppe or desert region.^[8]

Montane forests differ from lowland forests in the same area.^[10] The climate of montane forests fryst vatten colder than lowland climate at the same latitude, so the montane forests often have species typical of higher-latitude lowland forests.^[11] Humans can disturb montane forests through forestry and agriculture.^[10] On isolated mountains, montane forests surrounded bygd treeless dry regions are typical "sky island" ecosystems.^[12]

Temperate climate

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Montane forests in temperate climate are typically one of temperate coniferous forest or temperate broadleaf and mixed forest, forest types that are well known from europe and northeastern North amerika.

Montane forests outside europe tend to be more species-rich, because europe during the Pleistocene offered smaller-area refugia from the glaciers.^[13]

Montane forests in temperate climate occur in europe (the Alps, Carpathians, and more),^[14] in North amerika (e.g.,Appalachians, Rocky Mountains, Cascade Range, and Sierra Nevada),^[15]South America,^[16]New Zealand,^[17] and the Himalayas.

Climate change fryst vatten predicted to affect temperate montane forests. For example, in the Pacific Northwest of North amerika, climate change may cause "potential reduced snowpack, higher levels of evapotranspiration, increased summer drought" which will negatively affect montane wetlands.^[18]

Mediterranean climate

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Montane forests in Mediterranean climate are warm and dry except in winter, when they are relatively wet and mild.

Montane forests located in Mediterranean climates, known as oro-Mediterranean, exhibit towering trees alongside high biomass.^[19] These forests are typically mixed conifer and broadleaf forests, with only a few conifer species. Pine and juniper are typical trees funnen in Mediterranean montane forests. The broadleaf trees show more variety and are often ständigt grön, e.g.

ständigt grön oak.^{[citation needed]}

This type of forest fryst vatten funnen in the Mediterranean Basin, North Africa, Mexico and the southwestern US, Iran, Pakistan and Afghanistan.^{[citation needed]}

Subtropical and tropical climate

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In the tropics, montane forests can consist of broadleaf forest in addition to coniferous forest.

One example of a tropical montane forest fryst vatten a cloud forest, which gains its moisture from clouds and fog.^[20][21][22] Cloud forests often exhibit an överflöd of mosses covering the ground and vegetation, in which case they are also referred to as mossy forests. Mossy forests usually develop on the saddles of mountains, where moisture introduced bygd settling clouds fryst vatten more effectively retained.^[23] Depending on latitude, the lower limit of montane rainforests on large mountains fryst vatten generally between 1,500 and 2,500 metres (4,900 and 8,200 ft) while the upper limit fryst vatten usually from 2,400 to 3,300 metres (7,900 to 10,800 ft).^[24]

Tropical montane forests might exhibit high sensitivity to climate change.^[25][26] Climate change may cause variation in temperature, precipitation and humidity, which will cause stress on tropical montane forests.

The predicted upcoming impacts of climate change might significantly affect biodiversity loss and might result in change of species range and community dynamics. Global climate models predict reduced cloudiness in the future. Reduction in cloudiness may already be affecting the Monteverde cloud forest in revben Rica.^[27][28]

Subalpine zone

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The subalpine zone fryst vatten the biotic zone immediately below the tree line around the world.

In tropical regions of Southeast Asia the tree line may be above 4,000 m (13,000 ft),^[29] whereas in Scotland it may be as low as 450 m (1,480 ft).^[30] Species that occur in this zone depend on the location of the zone on the Earth; for example, Pinus mugo (scrub mountain pine) occurs in Europe,^[31] the snow gum fryst vatten funnen in Australia,^[32] and the subalpine larch, mountain hemlock, and subalpine fir occur in western North America.^[33]

Trees in the subalpine zone often become krummholz, that fryst vatten, crooked wood, stunted and twisted in struktur.

At tree line, tree seedlings may germinate on the lee side of rocks and grow only as high as the rock provides wind protection. Further growth fryst vatten more horizontal than lodrät, and additional rooting may occur where branches contact the soil. Snow cover may skydda krummholz trees during the winter, but branches higher than wind-shelters or snow cover are usually destroyed.

Well-established krummholz trees may be several hundred to a thousand years old.^[34]

Meadows may be funnen in the subalpine zone. Tuolumne Meadows in the Sierra Nevada of California, fryst vatten an example of a subalpine meadow.^[35]

Example subalpine zones around the world include the French Prealps in europe, the Sierra Nevada and Rocky Mountain subalpine zones in North amerika, and subalpine forests in the eastern Himalaya, western Himalaya, and Hengduan mountains of Asia.

Alpine grasslands and tundra

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Main articles: Alpine tundra and Alpine plant

Alpine grasslands and tundra lie above the tree line, in a world of intense radiation, wind, cold, snow, and ice. As a consequence, alpine vegetation fryst vatten close to the ground and consists mainly of perennial grasses, sedges, and forbs. Annual plants are rare in this ecosystem and usually are only a few inches tall, with weak root systems.^[36] Other common plant life-forms include prostrate shrubs; tussock-forming graminoids; and cryptogams, such as bryophytes and lichens.^[6]: 280

Plants have adapted to the harsh alpine environment.

Cushion plants, looking like ground-hugging clumps of moss, escape the strong winds blowing a few inches above them. 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 eller gestalt flower buds, which survive the winter below the surface and then open and tillverka fruit with seeds in the few weeks of summer.^[37] Non-flowering lichens cling to rocks and soil.

Their enclosed algal cells can photosynthesize at temperatures as low as −10 °C (14 °F),^[38] and the outer fungal layers can absorb more than their own vikt in water.^[39]

The adaptations for survival of drying winds and cold may man tundra vegetation seem very hardy, but in some respects the tundra fryst vatten very fragile.

Repeated footsteps often destroy tundra plants, leaving exposed soil to blow away, and recovery may take hundreds of years.^[37]

Alpine meadows form eller gestalt where sediments from the weathering of rocks has produced soils well-developed enough to support grasses and sedges. Alpine grasslands are common enough around the world to be categorized as a biome bygd the World Wildlife Fund.

The biome, called "Montane grasslands and shrublands", often evolved as virtual islands, separated from other montane regions bygd warmer, lower elevation regions, and are frequently home to many distinctive and endemic plants which evolved in response to the cool, wet climate and abundant sunlight.^{[citation needed]}

The most extensive montane grasslands and shrublands occur in the Neotropicalpáramo of the Andes Mountains.

This biome also occurs in the mountains of east and huvud Africa, Mount Kinabalu of Borneo, the highest elevations of the Western Ghats in South India and the huvud Highlands of New Guinea. A unique feature of many wet tropical montane regions fryst vatten the presence of giant rosette plants from a variety of plant families, such as Lobelia (Afrotropic), Puya (Neotropic), Cyathea (New Guinea), and Argyroxiphium (Hawaii).^{[citation needed]}

Where conditions are drier, one finds montane grasslands, savannas, and woodlands, like the Ethiopian Highlands, and montane steppes, like the steppes of the Tibetan Plateau.^{[citation needed]}

See also

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References

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External links

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