Quantifying the effects of the plant canopy, plant roots, and biological soil crust on soil detachment by overland flow

The plant canopy, plant roots, and biological soil crusts play important roles in soil detachment by overland flow. This study aims to quantify and analyze the effects of the plant canopy, plant roots, and soil crust on soil detachment via in situ experiments. Two typical dominant species, Bothriochloa ischaemum (Linn.) Keng (an herb) and Sophora davidii (Franch.) Skeel (a shrub) on the Loess Plateau, China, were selected. Four treatments were denoted T0 (bare land), T1 (canopy + root + crust), T2 (root + crust), and T3 (root) and subjected to flow scouring with a discharge of 5 L min−1 on a 20° slope. The soil detachment rate (SDr) in all treatments decreased sharply in the first 3 min due to changes in the internal force of the soil particles. As the effects of the canopy, roots, and soil crust were subsequently superimposed, the SDr decreased by 87.42–93.42% compared with that of the bare land. The plant canopy, roots, and soil crust contributed 8.57–9.54%, 92.36–95.27%, and −1.90 to −3.84% of the soil detachment reduction (SDR), respectively. Additionally, the naturally restored herb roots decreased soil detachment by flowing water more significantly than shrub roots in the study area. The effects of canopy, roots, and soil crust on SDr in grassland were similar to those in shrubland. Roots played a crucial role in strengthening soil resistance to detachment. Although shrubland had a greater effect on soil detachment reduction than grassland, herbs are strongly recommended for reducing soil erodibility due to the greater erosion-reducing potential of roots and their drought resistance on the Loess Plateau.