紫花苜蓿和马唐根的生物力学性能及相关因素的试验研究

选择固土护坡植物时，植物根的抗拉强度是一项重要的力学指标。对豆科的紫花苜蓿和禾本科的马唐根的抗拉力和纤维素含量的研究表明，根的抗拉强度和纤维素含量均与直径呈显著的负相关关系，根的抗拉强度与纤维素含量呈正相关关系，表明“木本植物根的抗拉强度、直径和纤维素含量关系”的研究结论在这两种草本植物上也同样适用。对紫花苜蓿和马唐根的抗拉强度与其“木质素/纤维素”之间关系的研究表明，两者呈负相关关系，证实纤维素含量对于维持根抗拉强度的作用大于木质素含量。研究发现，豆科紫花苜蓿根的应力-应变为对数函数关系，不符合胡克定律，马唐根的应力-应变关系的本构方程基本遵从胡克定律。直径愈小，紫花苜蓿和马唐根的应力—应变关系对应变率敏感程度愈高，根的极限延伸率愈大。另外，根的抗拉力和直径测试设备的改进，实验结果更准确可靠。这方面研究对揭示植物根系提高土壤抗冲击性和抗剪强度机理，更好地进行水土保持植物的选择和优化组合具有重要意义。

Experimental study on root bio-mechanics and relevant factors of Medicago sativa and Digitaria sanguinalis

Root tensile strength is an important factor to be considered when choosing suitable species for reinforcing soil on unstable slopes. Experiments were conducted for testing root tensile strength and measuring root cellulose content of Medicago sativa and Digitaria sanguinalis. Results indicated that in the two species, both the tensile strength and percentage of cellulose were negatively correlated with root diameter, while a positive correlation was found between percentage of cellulose and tensile strength. The conclusion confirmed that the relationship among root tensile strength, root diameter and root cellulose content found in tree root system was held also in the two species. The research demonstrated also a negative relationship between tensile strength and root lignin/cellulose ratio, and the influence of cellulose content was greater than that of lignin content on root tensile strength. There exists a logarithm relationship between stress and strain for Medicago sativa root, which does not follow Hooker's Law, and Digitaria sanguinalis root follows the Law. The experiment also testified that both the sensitiveness of stress-strain and critical strain increased with the decreasing root diameter. With improved root tensile force and diameter test apparatus, the experimental results were more reliable and accurate. The present research gained an insight into the soil reinforcement mechanism of the herb root system and the selection and of plant species for the purpose of soil and water conservation.