EFFECTS OF TRAMPLING AND VEGETATION REMOVAL ON SPECIES-DIVERSITY AND MICROENVIRONMENT UNDER DIFFERENT SHADE CONDITIONS

The effects of disturbance by trampling and vegetation removal on herb aceous communities and heir microenvironments were examined at two sit es with different levels of shade. The dominant species of the origina l vegetation were the perennial herb Artemisia princeps at the sunny s ite and the dwarf-bamboo Pleioblastus chino at the shady site. With no disturbance and marked dominance of these species, diversity was low. After vegetation removal there was a rapid recovery, leading to a mor e diverse vegetation with many more species, each with a lower dominan ce. Continuous trampling induced a short vegetation while the light in tensity under the foliage was increased. At the sunny site, species ri chness was depressed by trampling because the soil water potential dec reased markedly during summer and only the stress-tolerant annual Digi tal ia adscendens grew vigorously. Thus, the lowest species diversity was observed in the heavily trampled vegetation in late summer. At the shady site, soil water availability was not affected by trampling. Th is allowed the survival of many species and prevented a strong decline in diversity. The results suggest that the pattern of change in diver sity in communities subjected to various disturbances, was always dete rmined by the original environments.