Reforestation of degraded soil can improve soil quality through litter fall,but little is known about interactions between soil microbial biomass and soil physical and chemical properties.The objectives of this study are to determine effects of litter fall on physical and chemical properties and microbial biomass of a degraded soil 18 years after reforestation of Pinus massoniana and to analyze controlling factors on change in soil microbial biomass.Compared with the plot of eroded bare land,the reforested plot showed significant improvement in its measured soil properties,including soil porosity,proportion of water stable aggregate(> 0.25 mm),soil organic carbon and total nitrogen and soil microbial biomass irrespective of whether litter was removed or not.Magnitude of the increases varied with soil depth,slope position and litter management,being larger in the surface than subsurface soils,on the hilltop and foot-slope than on the middle slope.Compared with the treatment of litter preservation,the treatment of litter removal resulted in lower magnitude of the increases.Path analyses showed soil organic carbon content,was the most important factors affecting soil microbial biomass,followed by soil porosity,and then litter,which had some indirect effect through its contribution to soil porosity and soil organic carbon content.The findings of the study suggest that improving soil structural properties is important to recovery of soil microbial biomass.