Effects of different vegetation components on soil erosion and response to rainfall intensity under simulated rainfall

Vegetation effectively prevents soil erosion, however, the reductions in runoff and erosion caused by the different components of vegetation are unclear. Under simulated rainfall intensities (60, 90, and 120 mm h−1) and litter amount (5, 15, and 25 g m−2), five different treatments were established: intact grass (IG), litter and roots (LR), canopy and roots (CR), only litter (OL), only roots (OR), and a control bare plot (CK). The effects of the canopy, roots, and litter on erosion were quantitatively analysed. (1) The runoff rate and erosion rate were reduced by different treatments, and the IG treatment most effectively reduced runoff and sediment, followed by the LR, OL, CR, and OR treatments. (2) The velocity, runoff, and sediment reductions by litter were optimal. The velocity and runoff reduction effects of the roots were stronger than those of the canopy, reducing the sediment reduction more than the litter at 5 g m−2. The velocity, runoff, and sediment reductions produced by the canopy were weak, providing average contributions of 11.40%, 8.01%, and 7.34%, respectively. The vegetation more strongly affected sediment than runoff reduction. (3) Different treatments most effectively reduced runoff and sediment under a 60 mm h−1 rainfall. The contributions of the canopy, roots, and litter to reducing runoff and sediment decreased with increasing rainfall intensity. (4) Erosion rate and shear stress showed a linear relationship. The soil erodibility Kr and critical runoff shear stress τc of the IG plot were lowest and highest, respectively. Litter and roots decreased Kr and increased τc, respectively. Compared with the bare plot, Kr decreased by 44.44%–61.54% and 15.38%–40.74% and τc increased by 3.85%–7.44% and -1.65% to 7.69% in litter and roots, respectively. This study provides insights regarding the mechanism through which vegetation controls erosion and effective scientific basis for rational vegetation allocation.