Arctic vegetation

In the Arctic, the low tundra vegetation clothes a landscape of wide vistas, lit by the low-angle light characteristic of high latitudes. Much of the Arctic shows little impact from human activities, making it one of the few places on earth one can see intact ecosystems. Those who have had the luck to spend time in the Arctic have felt the incredible beauty of these landscapesfact|date=September 2008. Though the climate can be harsh, and the open expanses can seem stark and lonely, Nature’s strength can be seen in the delicate flowers that grow in sheltered cracks, in the caribou that floatfact|date=September 2008 through bitter storms, their feet lost in the ground blizzard (snow blowing along the ground), in the caterpillars that may have to grow through 14 summers before they are big enough (have stored enough energy) to be able to turn into moths [ [http://www.geog.ubc.ca/itex/library/manual/ITEXchapter9.pdf "Gynophora groenlandica"] ] .

Arctic plants are adapted to short, cold growing seasons [Saville, D. B. O., 1972: "Arctic adaptations in plants". Monograph No. 6, Research Branch, Canada Department of Agriculture, 81 pp.] . They have the ability to withstand extremely cold temperatures in the winter (winter hardiness), but what is even more important is the ability to be able to function in limiting summer conditions.

Arctic plants have a compressed growing season: they initiate growth rapidly in the spring, and flower and set seed much sooner than plants that grow in warmer conditions. Their peak metabolic rate also occurs at a much lower temperature than plants from farther south. Compact cushions of vegetation keep the plants close to the warm soil and shield the tender central growing shoot. The height of Arctic plants is also governed by snow depth. Plants that protrude above the snow are subject to strong winds, blowing snow, and being eaten by caribou, muskox, or ptarmigan. Mosses and lichens are common in the Arctic. These plants have the ability to stop growth at any time and resume it promptly when conditions improve. They can even survive being covered by snow and ice for over a year [ [http://library.thinkquest.org/C0113340/text/biomes/biomes.tundra.plants.adaptations.html ThinkQuest.org] ] .

Arctic bioclimate subzones

Arctic vegetation is largely controlled by summer temperatures. Mean July temperature is close to 0°C in the coldest areas. At these temperatures, plants are at their metabolic limits, and small differences in the total amount of summer warmth make large difference in the amount of energy available for maintenance, growth and reproduction. As one goes for north to south, the size, horizontal cover, abundance, productivity and variety of plants increases. These changes can be used to divide the Tundra Bioclimate Zone into 5 Subzones, A-E [Elvebakk, A., 1999: Bioclimate delimitation and subdivisions of the Arctic. In Nordal, I. and Razzhivin, V. Y. (eds.), "The Species Concept in the High North - A Panarctic Flora Initiative". Oslo: The Norwegian Academy of Science and Letters, 81-112.] . Subzone A, where mean July temperatures are less than 3°C, has no woody plants or sedges. Woody plants first occur in Subzone B (mean July temperature about 3-5°C) as prostrate (creeping) dwarf shrubs, and increasing in height up to 15 cm in Subzone C (about 5-7°C), to erect dwarf shrubs ( up to 40 cm tall) in Subzone D (mean July temperature about 7-9°C), and low shrubs (40 cm to 2 m tall) in Subzone E (mean July temperature about 9-12°C). At the treeline, where mean July temperatures are between 10 and 12°C, woody shrubs up to 2 m tall are abundant. The number of vascular plants in local floras available to form plant communities increases from fewer than 50 species in the coldest parts of the Arctic to as many as 500 species near treeline.

Circumpolar Arctic vegetation map

A circumpolar map of 15 different Arctic types was created by an international team of vegetation scientists, representing the six countries of the Arctic: Canada, Greenland, Iceland, Norway, Russia and the United States [CAVM Team, 2003: Circumpolar Arctic Vegetation Map, scale 1:7 500 000, Conservation of Arctic Flora and Fauna (CAFF) Map No. 1. Anchorage, Alaska: U.S. Fish and Wildlife Service] [ [http://www.arcticatlas.org Arctic Atlas] ] .

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