Vegetation restoration has significantly changed the rainfall-runoff process in the watershed, but its impact mechanism is still unclear. Under simulated rainfall conditions the runoff processes of surface and subsurface with different Pinus tabulaeformis litter cover densities (0, 300, 600, 900 g/m2) were investigated, and the effects of litter cover on the runoff generation mechanism were analyzed. The results showed that: (1) As the litter cover increased, the starting time of surface runoff significantly delayed, and the runoff amount has gradually decreased. Compared with the bare soil slope, the starting time of surface runoff for litter covered slope was delayed by 3 ~ 8 times and the runoff amount was decreased by 12.38% ~ 53.73%. (2) The bare soil slope did not generate subsurface runoff, but the subsurface runoff occurred on the litter covered slopes.The subsurface runoff amount increased with the increasing litter cover,and the maximum ratio of subsurface runoff to the total runoff for the 900 g/m2 cover slope reached 12.45%. (3) For litter covered slopes, the subsurface runoff generally occurred during the first 0.5~1 hours after the beginning of rainfall, and lasted for 7~9 days. The peak subsurface runoff rate occurred within 1~2 hours after the end of rainfall, and the peak values increased with the increasing litter cover. The results can help provide a scientific basis for analyzing the effects of vegetation cover on hillslope hydrological processes.

surface runoff; subsurface runoff; vegetation litter; simulated rainfall