Mediterranean Type Ecosystems pp 11-19
Distribution and Peculiarity of Mediterranean Ecosystems
The lands of mediterranean scrub or chaparral climate and the ecosystems that have developed in them must be defined in climatic terms. If we attempt to focus on the characteristic core of a mediterranean scrub or chaparral climate three terms stand out, two involving precipitation and one temperature. The most distinctive term involves the concentration of rainfall in the winter half year, November through April in the northern hemisphere and May through October in the southern. Although at a large number of stations, especially in California and Chile, 80 or even 90% of the precipitation occurs in winter, so large a proportion rarely obtains around the Mediterranean Basin itself. The value of at least sixty five percent of the year’s precipitation occurring in the winter half year seems, on the basis of examining a considerable number of station records, to form a satisfactory boundary. Winter rainfall, because of lower evaporation, is more effective in sustaining plant growth than is warm season precipitation; nonetheless, in this climatic region all but favorably located phreatophytic vegetation is subject to drought stress in summer.
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