6. AcknowledgmentsThis research was

6. Acknowledgments
This research was supported by program of the United States Department of Agriculture (Agreement Number: 58-6408-3-001FN) and the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, In- stitute of Water and Soil Conservation, Chinese Academy of Sciences and Ministry of Water Resources (No. 10,501-298). The authors greatly appreciate the help by Chinese Academy of Sciences Resource and Environment Science Data Center in providing partial land use data in the research project.