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Shrub patches often support the colonizers particularly under stressful and/or disturbed environments. The intensities of stresses and disturbances on mountains are often related to an elevation gradient and are decreased by shrub patches (canopy and litter). We aim to clarify these relationships by using shrub patches at different elevations on a volcano. We monitored all shoots in plots established inside and outside of patches of Salix reinii (Salicaceae) and their related environments, such as temperature, light, moisture and chemistry, at three elevations on Mount Koma (1131 m a.s.l.), northern Japan, from early spring in 2005 to summer in 2006. The patch structures were evaluated by area, branch density and litter thickness. The structures of shrub patches did not differ among the elevations. The patches increased the diversity of rare species, by an overall increase in plant species richness. The moisture, nitrogen and phosphate contents in the patches were higher than outside of patches. The effects of shrub patches on the cohabitants were overall positive, although the effects were negative on seedling abundance, shoot survival and flowering. These results suggest that the growth patterns of shrub patches determine the plant community structures and facilitate plant diversity. |
