不同植被空间配置下的坡面产沙及泥沙连通性变化特征

Variation Characteristics of Slope Sediment Yield and Sediment Connectivity Under Different Vegetation Spatial Distributions

植被是影响土壤侵蚀的重要因子,探讨坡面产沙和泥沙连通性对植被分布的响应对揭示土壤侵蚀过程机理及预测坡面侵蚀具有重要意义。通过室内人工放水冲刷试验,分析3种植被布设位置(坡上、坡中、坡下)在不同冲刷流量(3.2,5.2 L/min)和不同覆盖度(0,30%,50%,70%)下的减沙效益,结合坡面产沙潜力指数探究植被覆盖影响下的泥沙连通性变化特征。结果表明:(1)从不同盖度下的平均减沙效益及其稳定性来看,植被布局的减沙效益随盖度变化,且坡下植被空间分布最优。随冲刷流量增加,不同植被布局间的减沙效益差距缩小;(2)当植被盖度≤30%时,冲刷流量对坡面产沙的影响贡献较大;随盖度增加,植被的影响贡献程度大于冲刷流量,成为影响坡面侵蚀的主要因素;(3)坡面产沙潜力指数在不同植被盖度和分布位置下表现出明显差异。随盖度增加,产沙潜力指数减小,泥沙连通性减弱;坡下布设植被相比坡上和坡中产沙潜力指数最小,泥沙连通性最弱。该指数与产沙量之间存在显著的正相关关系,即产沙潜力越大,泥沙连通性越强,产沙量越大。研究结果可为深入探索土壤侵蚀机理及植被的生态效益提供科学依据,为黄土高原地区的生态建设提供参考。

Vegetation is an important factor affecting slope soil erosion process,thus exploring the response of slope sediment yield and sediment connectivity to vegetation spatial distribution is of great significance to reveal the mechanism of soil erosion process and predict slope erosion.In this study,based on the indoor scouring experiment,the sediment reduction efficiency of three common slope vegetation distributions(upper slope,middle slope,lower slope)under different flow discharge(3.2 and 5.2 L/min)and vegetation cover(0,30%,50%and 70%)were analyzed.And a sediment connectivity index(the index of potential sediment yield)was used to explore the characteristics of sediment connectivity influenced by vegetation.The results showed that:(1)The sediment reduction efficiency of vegetation distribution varied with the coverage.According to the average and variable amplitude of sediment reduction efficiency,the effect of vegetation distribution on the lower slope was best compared with other vegetation distribution.However,its gap in different vegetation distribution was reduced with the increase of the flow discharge.(2)The effects of flow discharge on sediment yields were slightly greater than that of vegetation when the vegetation cover was smaller(≤30%).But the role of vegetation enhanced gradually and became the dominant influencing factor with the increase of vegetation cover.(3)The index of potential sediment yield was significantly different under varied vegetation cover and distribution.As the vegetation cover increased,the index decreased and the sediment connectivity weakened.And the index of vegetation distribution on the lower slope was smallest and its sediment connectivity was worst compared with that on the upper or middle slope.In addition,there was significant positive correlation between the index of potential sediment yield and sediment yields,that is,the greater potential of sediment yield meant the stronger sediment connectivity and thus the greater sediment yields.The results can provide scientific basis for the exploration of soil erosion mechanism and ecological benefits of vegetation,and further provide reference for ecological construction in the Loess Plateau.