Because of the contrastive differences in environment and species composition, climatic amelioration may affect alpine vegetation differently between fellfield and snowbed communities. To test this prediction, the effects of warming on plant growth and vegetation structure were studied in two fellfield and two snowbed communities in northern Japan over 7 years using open-top-chambers (OTCs). OTCs increased the temperature by 1.1-1.8 °C, but the effects on snowmelt time and soil moisture were small. Vegetation height and canopy volume increased substantially at both fellfield sites as a result of the use of OTCs. Deciduous shrubs increased substantially at the lower fellfield and graminoids increased at the upper fellfield. In contrast, the responses of snowbed plants to OTCs were not significant. Because snowbed plants are snow-covered until mid-summer, climatic amelioration during the snow-free period may influence plant growth only slightly if the snow-free period does not change. Species richness and diversity were not changed by OTCs at any of the sites, indicating that the effect of warming alone may not be strong enough to change the species composition and diversity over several years. These results indicate significant variation in the response among alpine communities to warming.
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