Effects of undergrowth litter layer on runoff and sediment reduction under simulated rainfall conditions

The indoor simulated rainfall experiment was used to quantify the effects of litter coverage on runoff and soil erosion processes under different slope gradients and rainfall intensity conditions. The main results were as the followings: 1) the more the litter biomass in unit area was, the later the slope initial runoff generated. Besides, the effect of litter coverage on putting off runoff generation was better under 30 mm/hour rainfall intensity than 60 mm/hour. 2) Slope total runoff decreased with litter biomass in unit area increased. Compared with bare slope, the total runoff under rainfall intensities of 30 and 60 mm/hour decreased by 4.8%~54.8%, 4.2%~26.8%, respectively. Obviously, the effect of litter reducing runoff was better under 30 mm/hour rainfall intensity than 60 mm/hour. 3) Both slope sediment yield rate and total sediment yield decreased with litter biomass in unit area increased. Compared with bare slope, the total sediment yield could decrease by 56.2%~68.0% when the litter biomass in unit area was 50 g, while, when the litter biomass in unit area reached 200 g, the total sediment yield could drop over 92.2%. In particular, litter layer could still play an important role in sediment reduction when the rainfall intensity was 60 mm/hour. 4) Litter layer has a better effect on reducing sediment than reducing runoff. On the slope with litter coverage, the sediment yield maybe quite little when the runoff was rich. Experiment showed that to take full advantage of litter layer in soil and water conservation function, litter biomass in unit area had to reach more than 250 g.