Impacts of Human Disturbances on Riparian Herbaceous Communities in a Chinese Karst River

Riparian zones suffer from increased human disturbances and the plant communities change unpredictably in response to altered conditions. It is important to understand the effects of human activities on plant communities for rational tourism development and ecological protection programs. We sampled 14 and 27 sites in nearly natural and human-influenced landscapes along the Lijiang River in southwest China, respectively, to detect human impacts on the ecosystem. We set three survey lines, based on a submersion gradient, at each site to determine whether herbaceous species richness increased with distance from the river, and we examined the effects of disturbance on herbaceous distribution. The landscapes shared 101 common species, and unique species in the human-influenced landscape were partly synanthropic. The species richness and diversity indices of the nearly natural landscape were significantly higher than those of the human-influenced landscape (P < 0.01). Species richness increased with distance from the river in the nearly natural landscape, and a significant difference was detected among the variances of survey lines (P < 0.05) in the human-influenced landscape. In the nearly natural landscape, species richness increased with fewer hydrological effects, and a stable community was maintained. However, human disturbances led to community variability and fragmented riparian habitats, resulting in species extinction and ecological degradation. We suggest that appropriate dam and reservoir regulations, prohibition of soil destructions, and a long-term research program for ecosystem protection may help in improving the monitoring of human influences and sustainable management in riparian zones of tourist rivers.