|
The Holdridge life zones system is a global bioclimatic scheme for the classification of land areas. It was first published by Leslie Holdridge in 1947, and updated in 1967. It is a relatively simple system based on few empirical data, giving objective mapping criteria.〔(Western Ecology Division | US EPA )〕 A basic assumption of the system is that both soil and climax vegetation can be mapped once climate is known. ==Scheme== While it was first designed for tropical and subtropical areas, the system applies globally. The system has been shown to fit tropical vegetation zones, Mediterranean zones, and boreal zones, but is less applicable to cold oceanic or cold arid climates where moisture becomes the determining factor. The system has found a major use in assessing the possible changes in natural vegetation patterns due to global warming. The three axes of the barycentric subdivisions are: * precipitation (annual, logarithmic) * biotemperature (mean annual, logarithmic) * potential evapotranspiration ratio (PET) to mean total annual precipitation. Further indicators incorporated into the system are: * humidity provinces * latitudinal regions * altitudinal belts Biotemperature is based on the growing season length and temperature. It is measured as the mean of all temperatures above freezing, with all temperatures below freezing and above 30 °C adjusted to 0 °C, as plants are dormant at these temperatures. Holdridge's system uses biotemperature first, rather than the temperate latitude bias of Merriam's life zones, and does not primarily consider elevation. The system is considered more appropriate to the complexities of tropical vegetation than Merriam's system. 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「Holdridge life zones」の詳細全文を読む スポンサード リンク
|