LV Chun-juan1,2,CHEN Li-hua1,ZHOU Shuo1,SONG Heng-chuan1,GAI Xiao-gang1,Ji Xiao-dong1,Zhang Xin-ping3(1.Key Laboratory of Soil and Water Conservation and Desertification of Education Ministry,College of Water and Soil Conservation,Beijing Forestry University,Beijing 100083,2.College of Resources & Environmental Science,Shanxi Agriculture University,Taigu,Shanxi 030801,3.College of Water Conservancy and Civil Engineering,China Agricultural University,Beijing 100083)