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In order to prevent soil erosion in southern China,a study was performed to determine the drivers of sediment concentration variation using simulated rainfall and four soil management systems under field condition.Four soil management systems,i.e.,forest and grass coverage(FG),forest coverage with disturbed soil surface(FD),contour tillage(CT)and downslope tillage(DT),were exposed to two rainfall intensities(40 and 54 mm h-1)using a portable rainfall simulator.The drivers of sediment concentration variation were determined by the variations of runoff rate and sediment concentration as well as their relationships.The effects of the four soil management systems in preventing water and soil losses were compared using runoff rates and sediment concentrations at steady state.At runoff initial stage,sediment concentration variation was mainly driven by rainfall and management.The degree of sediment concentration variation driven by flow varied with different soil management systems.Three best relationships between runoff rate and sediment concentration were identified,i.e.,reciprocal(CT),quadratic(FG and FD)and exponential(DT).At steady state,runoff rates of the four soil management systems varied slightly,whereas their sediment concentrations varied greatly.FG and CT were recommended as the best soil management systems for preventing water and soil losses.