1. State Key Lab. of Soil Erosion and Dryland Farming on the Loess Plateau; Inst. of Soil and Water Conservation CAS and MWR; Yangling Shaanxi Province 712100 PR China
2. College of Environmental Science and Engineering Hunan Univ.; Changsha 410082 PR China
3. Key Lab. of Environmental Biology and Pollution Control; Hunan Univ. Ministry of Education; Changsha 410082 PR China
4. College of Tourism Historical Culture Southwest Univ. for Nationalities; Chengdu 610041 PR China