1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Northwest A&F University Yangling China
2. Institute of Soil and Water Conservation Chinese Academy of Sciences and Ministry of Water Resources Yangling China
3. Department of Land, Air and Water Resources Biogeochemistry and Nutrient Cycling Laboratory University of California, Davis Davis CA USA
4. Faculty of Geographical Science Beijing Normal University Beijing China