摘要:为探索地埂篱在喀斯特坡地水土保持中的价值，在重庆市酉阳县喀斯特顺层坡种植拉巴豆地埂篱，通过对根系灰度扫描、化学成分（木质素、纤维素、半纤维素）测定，单根抗拉试验和根-土复合体抗剪/冲试验，分析拉巴豆地埂篱根及根-土复合体的力学特性及影响因素。结果表明：（1）拉巴豆根系全根指标根长、根表面积、根体积、根重均表现为中坡 > 下坡 > 上坡，优势径级为0.0<d≤1.0 mm径级。全根根系纤维素的平均含量较木质素、半纤维素高，且与根系直径呈显著负相关。（2）根系平均极限抗拉力6.77 N、平均抗拉强度29.57 MPa。极限抗拉力与木质素含量呈对数函数正相关、与木质素/纤维素（木纤比）呈线性正相关，抗拉强度与纤维素含量、木纤比分别为对数函数正相关和负相关。（3）上坡位抗剪土样的根体积密度、根重密度和木纤比显著大于中、下坡；而抗冲土样的根体积密度、根重密度、纤维素和半纤维素含量则中坡较优，但不显著。（4）根系能有效提高土体抗剪性能，根-土复合体的内摩擦角与粘聚力均较对照裸地高，但仅上坡粘聚力存在显著性差异（较对照增大45.67%）。内摩擦角和抗冲指数均中坡、下坡较优，粘聚力最优值位于上坡位。根-土复合体的力学特性主要受根体积、根重、根表面积密度和纤维素的影响。综上，拉巴豆根及根-土复合体的力学特性主要贡献径级为0.0<d≤1.0 mm径级，中、下坡细根量大且根-土复合体抗冲性能表现较优，上坡根-土复合体抗剪切能力最强，但抗冲性能较弱。在推广拉巴豆地埂篱时，尽量种植于地势较低缓的中、下坡，更能凸显水土保持效益。



Abstract:To explore the effect of Dolichos lablab L. hedgerows on soil and water conservation, we planted Dolichos lablab L. at up, middle, and down slopes at bedding slopes of the karst valley in Youyang Chongqing. The roots and root-soil matrix were sampled. The mechanical properties of roots, soil anti-scourability, and soil shear strength of root-soil matrix were tested. To find the factors affecting mechanical properties, we scanned root grayscale and tested root chemical compositions (lignin, cellulose, and hemicellulose), and also performed correlation analysis. The results showed that:(1) The whole root parameters (root length, root surface area, root volume, and root weight) had the highest value in the middle slope portion, followed by down slope portion; the corresponding value of the up slope portion was minimum. Root dominant diameter was in the range of 0.0<d≤1.0 mm. The average content of cellulose in plant root was higher than that of lignin and hemicellulose. The root cellulose content was significantly negatively correlated with root diameter. (2) The root average ultimate tensile force of Dolichos lablab L. was 6.77 N and the average tensile strength was 29.57 MPa. Cellulose and lignin had statistically significant influences on the root mechanical properties. Their regression relations are as follows:the ultimate tensile force increased logarithmically with lignin content and increased linearly with lignin/cellulose(wood fiber ratio); tensile strength increased logarithmically with cellulose content, decreased logarithmically with wood to fiber ratio. (3) The root volume density, root weight density, and wood fiber ratio of the up slope shear strength samples were significantly greater than those of the middle and down slopes. However, for the anti-scour samples, root volume density, root weight density, cellulose content, and lignin content were higher at middle slope portions but there was no significant difference. (4) The root system could effectively improve the shear performance of the soil. The internal friction angle and cohesion of the root-soil matrix were higher than those of the bare ground control. Significant differences in cohesion was only observed for the up slope portion, between the terrace hedgerow and bare ground control, increasing by 45.67%. The internal friction angle and anti-scourability were better at middle and down slopes. Our study showed that the mechanical properties of the root-soil matrix were mainly affected by root volume density, root weight density, root surface area density, and cellulose content. In summary, the root diameter in the range 0.0<d≤ 1.0 mm substantially contributed to the mechanical properties of Dolichos lablab L. root and root-soil matrix. The anti-scourability of root-soil matrix was better at the middle and down slope portions; the shear performance of root-soil matrix was the best at the up slope portion, but anti-scourability was the worst. When promoting the planting of terrace hedgerows of Dolichos lablab L. soil and water conservation would be improved when they are planted in low and flat terrains (such as the middle and down slope portions).





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