Evaluating the Contribution of the Physical and Biochemical Effects of Root on Detachment for the Coarse-Textured Soil from the Three Gorges Reservoir, China

Plant roots have great effect on the process of soil detachment, but the contribution of the physical and biochemical effects of root on soil detachment have not been sufficiently evaluated. For the purpose to distinguish the relative contribution of the root physical effect and biochemical effect to soil erosion resistance, three kinds of treatment, soil samples without roots, dead roots and live roots, were chosen to simulate the condition of no root effect, the root's physical effect and the root's whole effect on the soil detachment, respectively. TheCynodon dactylonand purple soil in Three Gorges Reservoir Area in China were selected to conduct the scouring experiment under condition of five slope gradients (17.63%, 26.79%, 36.40%, 46.63% and 57.73%) and three runoff rates (1, 2 and 3 L min(-1)). The soil detachment process under different treatment conditions was analyzed. The effects of slope gradient and the runoff rate on soil detachment rate were also estimated for different treatment conditions and the contributions of the physical and biochemical effects of root on soil detachment were also evaluated. The results indicated that detachment rate showed a dramatically decrease initially, followed by gradual decrease until to a stable stage for all treatments. The soil detachment rate can be effectively described with the slope gradient and the runoff rate by using the power function, which was more influenced by slope gradient than by runoff rate for all the treatment conditions in this study. Plant roots could effectively diminish the soil detachment rate, and the contributions of physical and biochemical effects of root on detachment were 59.64%-82.09% and 17.91%-40.36%, with mean values of 68.92% and 31.08%, respectively. The root's physical effect is the main reason strengthens soil erosion resistance.