Spatial Variability of Soil Erosion and Soil Quality on Hillslopes in the Chinese Loess Plateau

Soil erosion rates and soil quality indicators were measured along two hillslope transects in the Loess Plateau near Yan'an, China. The objectives were to: (a) quantify spatial patterns and controlling processes of soil redistribution due to water and tillage erosion, and (b) correlate soil quality parameters with soil redistribution along the hillslope transects for different land use management systems. Water erosion data were derived from 1 3 7Cs measurements and tillage erosion from the simulation of a Mass Balance Model along the hillslope transects. Soil quality measurements, i.e. soil organic matter, bulk density and available nutrients were made at the same sampling locations as the 137Cs measurements. Results were compared at the individual site locations and along the hillslope transect through statistical and applied time series analysis. The results showed that soil loss due to water erosion and soil deposition from tillage are the dominant soil redistribution processes in range of 23-40 m, and soil deposition by water erosion and soil loss by tillage are dominant processes occurring in range of more than 80 m within the cultivated landscape. However, land use change associated with vegetation cover can significantly change both the magnitudes and scale of these spatial patterns within the hillslope landscapes. There is a strong interaction between the spatial patterns of soil erosion processes and soil quality. It was concluded that soil loss by water erosion and deposition by tillage are the main cause for the occurrence of significant scale dependency of spatial variability of soil quality along hillslope transects. Key wo rd s : Soil erosion. Soil quality. Cesium-137. Spatial va r i a b i l i t y. Loess Plateau. I N T RO D U C T I O N The spatial variability patterns of soil erosion and their impacts on soil quality within the landscape is being considered as a basis for making management decisions for s u s t a i n a ble cropping systems in China. Early estimation of the suspended sediment indicates that soil erosion in the Ye l l ow River Basin, China causes considerable losses of N, P and other soil nutrients. Howeve r, a serious gap in k n owledge about the spatial relationship between erosion and soil quality exists for the "homogenous loess soil" within changing landscape structure and vegetation cove r