Abstract: Based on the measured data and the model of plotted watershed hydrology, the benefit of sediment reduction by biological harnesses of soil and water conservation was studied in the watershed scale. The result indicated that the erosion modulus in Wangdonggou watershed, which were 1869t穔m², 1050t穔m², 383t穔m², and 504t穔m² in the periods of the sixth, seventh, eighth, and ninth five year plans, respectively, were gradually reduced by comprehensive measures. Taken out the effect of rainfall, the sediment reduction by biological measures of soil and water conservation was increased by 24.1% and 22.4% in the periods of eighth and ninth five year plans compared to that in the seventh five year plan.

Key words: Watershed scale, Soil and water conservation, Benefit of sediment reduction, successive rotation, Chaetomium globosmn ND35, poplar, photosynthesis, light use efficiency.