为解析黄土高原地区典型草地土壤分离能力变化的力学机制，选择代表性的须根系和直根系草地作为研究对象，基于室内径流冲刷试验，估算了相对土壤分离能力（RSD），测定了土壤抗剪强度和根系抗拉力，并基于Wu氏模型估算了根系黏聚力（C_r）。结果表明，须根系草地的RSD较直根系草地显著低77.27%，而Cr较直根系草地高14.84%。直根系草地的C_r对RSD的表达效果优于根长密度，而须根系草地效果差异不明显。RSD与200 KPa正应力下抗剪强度（τ₂₀₀）的相关性优于其他正压力。根土复合体中，C_r对土壤分离的效应强于τ₂₀₀。通过根土复合体力学参数能够有效预测直根系草地的土壤分离能力，但对于须根系草地的预测还需进一步探究。研究结果可为黄土高原根系减蚀机理的完善提供参考。

【Objective】This study aimed to understand the erosion mechanism of typical grassland in the Loess Plateau by analyzing the mechanical mechanism of soil detachment. 【Method】The representative grassland with tap roots and fibrous roots was selected as the research object in this study. Undisturbed soil samples were collected and subjected to flow scouring, and the relative soil detachment capacity (RSD) was calculated. The soil shear strength and root tensile force were determined, and the root cohesion was estimated based on Wu's model. 【Result】The RSD of grassland with fibrous roots was 77.27% significantly lower than that of grassland with tap roots, while the soil cohesion (C_r) was 14.84% higher than that of grassland with tap roots. The expression effect of C_ron RSD in the grassland with tap roots was better than that of root length density, and this effect was not obvious in the grassland with fibrous roots. The correlation between the RSD and soil shear strength under normal stress of 200 Kpa (τ₂₀₀) was better than the shear strength under other normal stresses. In the root-soil composite, the effect of C_ron soil detachment was stronger than that of τ₂₀₀. Additionally, the soil detachment capacity of the root-soil composite in the grassland with tap roots, could be effectively predicted by the mechanical parameters, but the prediction of soil detachment capacity in the grassland with fibrous roots need to be further explored. 【Conclusion】Thus, this study presents an effective way to analyze the soil detachment mechanism by mechanical properties of root-soil composites. The results could provide a reference for the study of the erosion reduction mechanism of roots in the Loess Plateau.

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国家自然科学基金项目（42307452，U2040208，42107352）资助