Distinguishing the effects of vegetation characteristics on soil erosion process on the loess plateau of China

Abstract

Vegetation restoration significantly decreases soil erosion. Although runoff shear stress is not divided into grain and form shear stresses, the dynamic mechanisms of soil erosion remain unclear. To explore the dynamic mechanisms of soil erosion, two herbaceous plants, namely, Bothriochloa ischcemum (Linn.). Keng (BI) and Artemisia vestita Wall. ex Bess (AG), were planted at six planting densities of 5, 10, 15, 20, 25 and 30 plants m⁻² to obtain different vegetation characteristics. A simulated rainfall experiment (rainfall intensity of 1 mm min⁻¹) was conducted on runoff plots (length and width of 2.0 and 0.5 m, respectively), and the flow velocity, runoff rate and soil loss rate were measured. The results showed that the grain and form shear stresses ranged from 0.04 to 0.16 and 1.40 to 3.88 Pa under six planting densities, respectively. Grain shear stress decreased with planting density in both BI and AG grasslands. The form shear stress exhibited a greater magnitude in BI grasslands at a lower planting density, whereas in AG grasslands, the highest form shear stress was observed at a planting density of 20 plants m⁻². Vegetation can significantly reduce soil loss. Compared with that in bare soil, soil loss amount in the BI and AG grasslands were 68.08 to 95.08% lower. The reduction in soil loss amount was enhanced by the increased planting density. The BI grasslands were more effective in reducing soil loss than the AG grasslands. The amount of soil loss was mainly influenced by the interaction between vegetation and runoff characteristics, which explained the majority of variation (49.48%). The total soil loss increased with increasing grain shear stress and decreased with increasing vegetation coverage, root collar area and soil organic matter as a power function. With increasing total runoff, total soil loss increased linearly. Finally, the amount of soil loss was simulated using the grain shear stress, root collar area, soil organic matter and total runoff. The performance of the model used in this study was satisfactory.