Effects of different vegetation litter cover on hydrodynamic characteristics of soil runoff-sediment yield in Taiyi Mountain area of northern China

Vegetation litter is effective in mitigating surface soil erosion caused by rainfall and runoff. Studying the runoff, sediment yield, and hydrodynamic characteristics of the soil covered by vegetation litter cover is crucial to understanding how vegetation litter cover affects soil erosion. To assess the impacts of different types of vegetation litter on soil erosion in the Taiyi Mountain area of northern China, Quercus acutissima Carruth. (QAC), Pinus densiflora Siebold & Zucc. (PDS), Vitex negundo var. heterophylla Rehd. (VNH), and Themeda japonica Willd. (TJW) litter covered soil were the research subjects, and no-litter covered soil was used as a control check (CK). The process of erosion of soil covered by different vegetation litter under different rainfall intensities (50, 75, and 100 mm/h) with 60 min of rainfall was studied. It was found that compared with CK, the runoff and sediment yield rates of litter-covered soil decreased by 18.95%–44.15% and 21.42%–60.16%, respectively. In terms of the effect on reducing the runoff and sediment yield rate, the performance is QAC > PDS > VNH > TJW. Under varying rainfall intensities, the patterns of runoff and sediment yield fluctuate as rainfall duration increases. Likewise, with the increase in rainfall intensity, the runoff yield rate and sediment yield rate also show an increasing trend. The runoff yield rate was increased by 3.21 and 1.49 times under 100 mm/h compared with 50 and 75 mm/h, respectively. Additionally, there were 16.56 and 1.44 times, respectively, and increases in the sediment yield rate. Hydrodynamically, litter cover increases the Darcy-Weisbach friction coefficient by 1.49–11.15 times, increases the shear stress threshold for initiating soil erosion by about 6.67%–38.01%. This further led to a reduction in the runoff flow velocity and stream power, by approximately 14.87%–67.26% and 7.38%–61.54%, respectively, thereby reducing the degree of soil erosion. The current research demonstrates that the characteristics of soil erosion and sediment yield under vegetation litter cover can be more accurately described by the stream power among the hydrodynamic parameters.