MICROLIMATIC AND VEGETATIONAL CONTRASTS WITHIN A SUBALPINE VALLEY

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Abstract
Great contrasts between climatic niches have been observed within the west-east-oriented, recently glaciated, topographically highly varied subalpine-alpine Slate Creek Valley east of Yosemite National Park. Temperature regimes obtain on opposite very steep slopes of the valley that simulate differences in latitude. During the brief 2-month growing season the daily temperature amplitudes varied between 4 and 15[degree] C on north slopes, and 2 and 28[degree] C on south slopes, whereas in the bottom of the valley temperature inversions caused frost most of the nights. The highly varied microclimates and edaphically distinct habitats are reflected in an unusually rich vegetation that consists of elements of arctic circumpolar, Pacific coastal, Great Basin-Rocky Mountain vegetations that have converged in this region. They have joined an endemic fell field vegetation that probably existed during the period of heaviest glaciation. These highly diverse elements find favorable habitats within the microclimatic and edaphic niches of this valley.