根系固土主导力学因素与差异性评价

为了探究影响根系固土的主导力学因素,并为侵蚀区固土抗蚀植物种的筛选提供部分依据。以3—4年生(4年生为主)5种内蒙古干旱、半干旱地区常见的水土保持植物:柠条(Caragana microphylla Lam.)、沙柳(Salix psammophila C.wang et Ch.Y.Yang)、沙地柏(Sabina vulgaris Ant.)、白沙蒿(Artemisia sphaerocephala Krasch.)、沙棘(Hippophae rhamnoides Linn.)为研究对象,针对春季土壤干旱和夏季暴雨(土壤湿润)两种自然条件,对影响5种植物根系固土的10项指标进行主成分分析。结果表明,根系抗拉力学特性是影响植物根系固土的主导力学因素,其次为根-土界面摩阻特性,最后是根-土复合体抗剪特性。在此基础上,从根系力学特性的角度出发,运用层次分析法对两个时期5种植物根系固土能力的差异性进行评价。在评价过程中,为了保证评价数据完整性,减小专家主观因素所带来的误差,使评价结果更具科学性,该文将两个时期主成分分析所得3个力学特性的方差贡献率作为权重。评价结果显示,根系固土指数为:春季土壤干旱时期,柠条(0.834)沙柳(0.330)沙地柏(-0.066)白沙蒿(-0.206)沙棘(-0.864);夏季暴雨时期分别为,柠条(0.876)沙地柏(0.218)沙柳(0.065)白沙蒿(-0.404)沙棘(-0.755)。5种植物中,柠条根系的抗拉力学特性显著优于其他植物,可作为干旱、半干旱地区固土抗蚀的重要参考树种。

Mechanical factors influencing soil-reinforcement by roots and identifying appropriate plant species for erosion control

Influenced by the physiological and genetic characteristics of plants, the mechanical properties of roots differ significantly, with the result that species vary in their ability to resist soil erosion. The selection of species to reinforce soil and prevent erosion is the key to improving not only soil and water conservation, but also vegetation and ecological restoration. Research to identify suitable plant species is still in its early stages, and studies addressing many issues are urgently needed. Caragana microphylla Lam, Salix psammophila C.wang & Ch.Y.Yang, Sabina vulgaris Ant, Artemisia sphaerocephala Krasch, and Hippophae rhamnides Linn are common plants used in soil and water conservation projects in the arid and semi-arid regions of Inner Mongolia. Rainfall is concentrated in summer with short-duration and high-intensity. The mechanical properties of roots differ significantly with growth period and soil moisture conditions. In order to study the mechanical factors influencing soil-reinforcement by roots and identify suitable anti-erosion plant species for this area, root tensile strength, root-soil surface friction, and root-soil composite shear strength of five plant species were studied. During the spring drought period and summer wet period, ten indicators of efficacy in erosion prevention (root-soil composite cohesion, root-soil composite equivalent friction angle, root-soil interface sheer strength, cumulative surface area, interface friction coefficient, representative root elasticity modulus, representative root constitutive properties, taproot tensile strength, lateral branch root tensile strength, length of cumulative root length) of the five species at the age of 3-4 (mainly 4) years were measured. The data were then analyzed using principal component analysis (PCA) with SAS9.0 software. The PCA results indicate that tensile mechanical strength had the greatest influence on soil reinforcement, followed by root-soil surface friction, and then root-soil composite shear strength. Based on these mechanical factors, the performance of the five species was evaluated. In order to maintain the integrity of the data and reduce uncertainty caused by subjective expert assessments, the variance contribution to the PCA of each of the three mechanical characteristics was used as to weight an analytic hierarchy process (AHP). The results showed the soil-reinforcement indices in the drought period were ranked Caragana microphylla Lam (0.834) > Salix psammophila C.wang et Ch.Y.Yang (0.303) > Sabina vulgaris Ant (-0.066) > Artemisia sphaerocephala Krasch (-0.206) > Hippophae rhamnides Linn (-0.864), while in the wet period they were ranked Caragana microphylla Lam (0.876) > Sabina vulgaris Ant (0.218) > Salix psammophila C.wang et Ch.Y.Yang (0.065) > Artemisia sphaerocephala Krasch (-0.404) > Hippophae rhamnides Linn (-0.755). The results suggest that species with better root tensile strength should be chosen reinforce soil and prevent erosion. Of the five species, Caragana microphylla Lam is the preferred soil-reinforcement and anti-erosion plant in arid and semi-arid regions due to its high root tensile strength.