1. Dep. of Soil and Water Sciences; China Agricultural Univ.; Key Lab. of Plant-Soil Interactions, MOE; Beijing 100094 P.R. China
2. State Key Lab. of Water Resources and Hydropower Engineering Science; Wuhan Univ.; Wuhan 430072
3. School of Environmental Science and Engineering, Sun Yat-Sen Univ.; Guangzhou 510275 P.R. China