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Snow patch is a geomorphological pattern of snow and firn accumulation which lies on the surface longer time than other seasonal snow cover. There are two types to distinguish; seasonal snow patches and perennial snow patches. Seasonal patches usually melt during the late summer but later than rest of the snow. Perennial snow patches are stable for more than two years and also have bigger influence to surroundings. (Demek, 1987). Snow patches often start in sheltered places where both thermal and orographical conditions are favourable for the conservation of snow such as small existing depressions, gullies or other concave patterns. Main process that creates these accumulations is called nivation. It is a complex of processes that includes freeze–thaw action (weathering by the alternate freezing and melting of ice), mass movement (the downhill movement of substances under gravity), and erosion by meltwater which is main agent of the surroundings influence. (Berrisford, 1991). There is high soil moisture around the snow patch that supports growing of specific vegetation. Snow patch vegetation is very distinctive. It is usually dominated by species that tolerate a shortened growing season and is predominantly herbaceous. With increasing duration of snow persistence, non – vascular plants predominated over vascular plants for example Salicetum herbaceae, Salix herbacea etc. (Wahren, Williams, Papst, 2001) ==Sources== *BERRISFORD, M.S. (1991): Evidence for enhanced mechanical weathering associated with seasonally late-lying and perennial snow patches, Jotunheimen, Norway, Permafrost and periglacial processes, vol. 2 *DEMEK, J. (1987): Obecná geomorfologie, Academia, Praha *WAHREN, C.-H.; WILLIAMS, R.J.; PAPST, W.A. (2001): Alpine and subalpine snow patch vegetation on the Bogong High Plains, SE Australia, Journal of vegetation science, vol.12 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Snow patch」の詳細全文を読む スポンサード リンク
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