中文摘要：

为探讨草本植物根系对崩岗洪积扇土壤抗剪强度的影响,以巨菌草（Pennisetum sp.）和宽叶雀稗（Paspalum wettsteinii）为研究对象,采用WinRHIZO根系分析系统对根系特征进行定量分析,并采用原位剪切试验测定崩岗洪积扇各土层的抗剪强度。结果表明：（1）根系能够改善土壤的结构及水分状况;（2）2种草本植物根系均主要分布在0—5cm土层,该层巨菌草根系各参数值是该草种根系均值的3.1～4.39倍,宽叶雀稗的则为2.23～2.57倍,随着土层深度的增加,巨菌草根系参数呈对数函数减小,而宽叶雀稗呈线性减小;（3）土壤抗剪强度均值大小表现为巨菌草〉宽叶雀稗〉裸地,其大小依次为21.04,16.43,9.89kPa;在0—20cm土层,2草种抗剪强度均显著大于裸地;（4）土壤抗剪强度与生物量密度、根表面积密度和分叉数密度极显著正相关,与根长密度显著正相关;巨菌草根系的生物量密度是表征土壤抗剪强度的最主要因子,而宽叶雀稗的则为根长密度。2种草本植物根系均能提高崩岗洪积扇土壤的抗剪强度,而巨菌草的效果优于宽叶雀稗。

英文摘要：

To study the effects of herbs＇ root systems on soil shear strength in a collapsing gully alluvial fan.Pennisetumsp.and Paspalum wettsteinii were chosen as the research objects.A root analysis system（WinRHIZO）was used to characterize the root systems,and the in-situ shearing test was applied to analyze soil shear strength.The results showed that：（1）Root systems could improve soil structure and water status.（2）Root systems of both herbal plants were mainly distributed in the 0-5cm soil layer,in which root parameters of Pennisetumsp.and Paspalum wettsteinii were 3.1to 4.39 times and 2.23 to 2.57 times as great as their average values in the whole soil profile,respectively.Root parameters of Pennisetumsp.and Paspalum wettsteinii showed a logarithmic and linear decrease with the increase of soil depth,respectively.（3）The average soil shear strength followed the order of Pennisetum sp.〉 Paspalum wettsteinii 〉bare land,being 21.04,16.43,and 9.89 kPa,respectively.In the 0-20 cm soil layer,shear strength of soil with two herbal plants were significantly greater than that of the bare land.（4）Soil shear strength had extremely significantly positive correlations with biomass density,root surface area density,and fork density（P〈0.01）,and it also had a significantly positive correlation with root length density（P〈0.05）.The most important factor of Pennisetumsp.to characterize soil shear strength was biomass density,while that of Paspalumwettsteiniiwas root length density.It is concluded that,root systems of both herbal plants could improve soil shear strength in the collapsing gully alluvial fan,and Pennisetumsp.was more effective than Paspalum wettsteinii.