1. Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University, Ministry of Education), Guilin 541004, P. R. China
2. School of Environment and Resource, Guangxi Normal University, Guilin 541004, P. R. China
3. University Key Laboratory of Karst Ecology and Environmental Change of Guangxi Province (Guangxi Normal University), Guilin 541004, P. R. China
4. School of Environmental and Chemical Engineering, Shanghai University, Shanghai, 200444, P. R. China