Quantifying the Binding and Bonding Effects of Plant Roots on Soil Detachment by Overland Flow in 10 Typical Grasslands on the Loess Plateau

Plant roots penetrating the soil may enhance soil resistance and protect the topsoil against scouring by overland flow, but their mechanisms are not fully understood. This study was performed to quantify the binding and bonding effects of plant root systems on the process of soil detachment by overland flow. Ten typical dominant species of herbage representing two different root architectures on the Loess Plateau were selected, and 900 soil samples were collected from these grasslands for detachment capacity measurements under different flow shear stresses. The results showed that the existence of plant root systems greatly reduced the soil detachment capacity by 53.6%, of which 41.4 and 12.2% were attributed to the root binding and bonding effects, respectively. The contribution rate of the binding and bonding effects depended on plant root architecture (i.e., the tap and fibrous roots). For tap root, the average contribution of the plant root for protecting soil from detachment was 41.6%, of which 33.2 and 8.4% were induced by the root binding and bonding effects. For fibrous root, the mean contribution of plant root was 65.7%, of which 49.7 and 16.0% were attributed to the root binding and bonding effects, respectively. Series correction coefficients that took into consideration the root binding and bonding effects of 10 typical dominant plants for their rill erodibility in the Water Erosion Prediction Project model on the Loess Plateau; the result was satisfactory with Nash-Sutcliffe efficiency coefficients that ranged from 0.48 to 0.58.