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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. 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.〔(ThinkQuest.org )〕
==Arctic bioclimate subzones==
Arctic vegetation is largely controlled by Temperature. Woody plants first occur in Subzone B (meaning 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 Sub zone 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 tree lines.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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