The mechanical property of soil-root composite is closely related to that of vegetation roots. Through random sam-pling in field plot,the root parameters and mechanical properties of Setaria viridis and Echinochloa crus-galli which are common annual herbaceous vegetations in China are tested. The test results show that during the sampling period,as growth duration gets longer,the root diameter and root density parameters of Setaria viridis initially increased and then decreased; root diameter and root mass density of Echinochloa crus-galli decreased continuously, whereas the root content increased and followed by a de-crease. The average root diameter of Setaria viridis is smaller than that of Echinochloa crus-galli, but has larger root content, root mass density,root length density,single root tensile capacities and tensile strengths;The single root tensile capacity and ten-sile strength of Setaria viridis and Echinochloa crus-galli are strongly and positively correlated with root diameter in a power function and negatively correlated in a logarithmic function significantly respectively( P≤0.001). Other than roots bigger than 0.6 mm in diameter,single root tensile capacity and root tensile strength of both vegetations go up first and then go down with the growth duration. The test result is useful to further understanding the dynamic changes of the mechanical properties of soil-root composite.%土壤-根系复合体力学性能与根系力学性能密切相关.通过野外小区随机取样,测定了一年野生草本植物 —狗尾巴草和稗草的根系参数和力学性能.结果显示:研究期间,狗尾巴草根系直径和根系密度参数随生长历时先增大后减小,稗草根系直径和根重密度随生长历时持续减小,而其含根量则随之先增大后减小;狗尾巴草根系直径小于稗草,但其含根量、根重密度、根长密度以及草根抗拉力和抗拉强度均大于稗草;两种植物单根抗拉力和抗拉强度分别与根系直径呈极显著幂函数正相关和对数负相关( P≤0.001),除较粗根系( > 0.6 mm)外,单根抗拉力和抗拉强度均随生长历时先增大后减小.试验结果有助于进一步了解土壤-根系复合体力学性能的动态变化特性征,以为固土护坡野生草本植物的选择提供一定理论依据.
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