page_title: Alpine tundra
section_title: Flora
hierarchical_section_title: Alpine tundra / Flora
caption_attribution_description: Deutsch: Der von Wollgras gesäumte Ablauf des Chüebodensees oberhalb von Elm, Kanton Glarus. Blick auf den Piz Sardona (3056m) und rechts davon auf die Tschingelhoren (2849 m). English: The outflow of the Chüebodensee close to Elm, Kanton Glarus. The snow-topped mountain is the Piz Sardona (3056m) and the peaks on the right, just before the rock spur blocks the sight are the Tschingelhoren (2849 m). Cotton-sedge in the foreground.
context_page_description: Alpine tundra is a type of natural region or biome that does not contain trees because it is at high elevation. As the latitude of a location approaches the poles, the threshold elevation for alpine tundra gets lower until it reaches sea level, and alpine tundra merges with polar tundra.
  The high elevation causes an adverse climate, which is too cold and windy to support tree growth. Alpine tundra transitions to sub-alpine forests below the tree line; stunted forests occurring at the forest-tundra ecotone are known as Krummholz. With increasing elevation it ends at the snow line where snow and ice persist through summer.
  Alpine tundra occurs in mountains worldwide. The flora of the alpine tundra is characterized by dwarf shrubs close to the ground. The cold climate of the alpine tundra is caused by adiabatic cooling of air, and is similar to polar climate.
context_section_description: Because the habitat of alpine vegetation is subject to intense radiation, wind, cold, snow, and ice, it grows close to the ground and consists mainly of perennial grasses, sedges, and forbs. Perennial herbs (including grasses, sedges, and low woody or semi-woody shrubs) dominate the alpine landscape; they have much more root and rhizome biomass than that of shoots, leaves, and flowers. The roots and rhizomes not only function in water and nutrient absorption but also play a very important role in over-winter carbohydrate storage. Annual plants are rare in this ecosystem and usually are only a few inches tall, with weak root systems. Other common plant life-forms include prostrate shrubs, graminoids forming  tussocks, cushion plants, and cryptogams, such as bryophytes and lichens.
  Relative to lower elevation areas in the same region, alpine regions have a high rate of endemism and a high diversity of plant species. This taxonomic diversity can be attributed to geographical isolation, climate changes, glaciation, microhabitat differentiation, and different histories of migration or evolution or both. These phenomena contribute to plant diversity by introducing new flora and favoring adaptations, both of new species and the dispersal of pre-existing species.
  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 flower buds, which survive the winter below the surface and then open and produce fruit with seeds in the few weeks of summer.
  Alpine areas are unique because of the severity and complexity of their environmental conditions. Very small changes in topography – as small as 1 foot (0.3 m) or less – may mean the difference between a windswept area or an area of snow accumulation, changing the potential productivity and plant community drastically. Between these extremes of drought versus saturation, several intermediate environments may exist all within a few yards of each other, depending on topography, substrate, and climate. Alpine vegetation generally occurs in a mosaic of small patches with widely differing environmental conditions. Vegetation types vary from cushion and rosette plants on the ridges and in the rock crannies; to herbaceous and grassy vegetation along the slopes; dwarf shrubs with grasses and forbs below the melting snowdrifts; and sedges, grasses, low shrubs, and mosses in the bogs and along the brooks.
  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, allowing exposed soil to blow away; recovery may take hundreds of years.
caption: An alpine mire in the Swiss Alps
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