Abstract: A study was carried out in the natural stands of Populus davidiana in the area of Loess plateau,northwestern China,to observe the hydrological and soil conservative function of litterfall.It was found that the amount of litterfall was the highest in October and the interception rate of litter reached 18.9%.Evaporation of soil water, which was restrained by litter and affected by soil moisture content,was reduced with the increment of the thickness of litter layer in the stands. The occurrence of streamflow varied directly with the thickness of litter layer and negatively with the degree of slope and the streamflow depth.The study also showed that soil loss damping was improved to 83.2% by 1cm thick layer of litter on the ground.the streamflow and sedimentation were increased by 1.66 and 8.15 times,respectively,as the litter was removed from the ground.

Key words: Populus davidiana, Litterfall, Hydrology, Soil and water conservation