A comparison of the effectiveness of the roots of two grass species in reducing soil erosion on alluvial fans in south‐east China. Issue 1 (11th September 2019) - Jiang, Fangshi
Abstract: The effects of root systems on soil detachment by overland flow are closely related to vegetation types. The objective of this study was to quantify the effects of two gramineous roots ( Paspalum mandiocanum with shallow roots and Pennisetum giganteum with deep roots) on soil detachment capacity, rill erodibility, and critical shear stress on alluvial fans of benggang in south‐east China. A 4‐m‐long and 0.12‐m‐wide flume was used. Slope steepness ranged from 9% to 27%, and unit flow discharge ranged from 1.39 × 10 −3 to 4.19 × 10 −3 m 2 s −1 . The mean detachment capacities of P. mandiocanum and P. giganteum lands were 18% and 38% lower than that of bare land, respectively, and the effects of root on reducing soil detachment were mainly reflected in the 0‐ to 5‐cm soil layer. The most important factors in characterizing soil detachment capacity were root length density and soil cohesion, and soil detachment capacity of the two grass lands could be estimated using flow shear stress, soil cohesion, and root length density ( NSE = 0.90). With the increase in soil depth, rill erodibility increased, whereas shear stress decreased. The mean rill erodibilities of P. mandiocanum and P. giganteum lands were 81% and 61% as much as that of bare land, respectively. Additionally, rill erodibilities of the two grass lands could be estimated as an exponential function by root length density and soil cohesion ( NSE = 0.88). The mean critical shear stress of P. mandiocanum and P. giganteum lands was 1.29 and 1.39 times that of bare land, respectively, and it could be estimated with a linear function by root length density ( NSE = 0.76). This study demonstrated that planting of the two grasses P. mandiocanum and P. giganteum could effectively reduce soil detachment and enhance soil resistance to erosion on alluvial fans, with the deep roots of P. giganteum being more effective than the shallow roots of P. mandiocanum. The results are helpful for understanding the influencing mechanism of root systems on soil detachment process. Abstract : Two grasses of Paspalum mandiocanum and Pennisetum giganteum could effectively reduce soil detachment of alluvial fan in south‐east China, and the effects of roots on reducing soil detachment capacities decreased with the increase in soil depth. Influences of reducing soil detachment by P. giganteum with deep roots were more effective than those by P. mandiocanum with shallow roots. The most important factors to characterize soil detachment capacity were the root length density and soil cohesion, which were negatively related to soil detachment capacity.