基于根系化学组成的抗拉力学特性分析

Tensile mechanical properties of roots based on chemical composition

【目的】分析根系力学特性与化学组成的关系,揭示根系固土的机理,为边坡的生态修复预测及树种优化提供理论基础。【方法】以贵州省石漠化土层浅薄地区乡土树种火棘(Pyracantha fortuneana)和刺鼠李(Rhamnus dumetorum Schneid)为研究对象,通过对根系木质素、纤维素和半纤维素含量及根系抗拉特性的测定,结合根系横截面的表观形态分析,从更为微观的角度分析根系固土护坡机制。【结果】根系力学性质与根径间存在明显的尺寸效应,根径越大,极限抗拉力越大,极限抗拉强度和极限延伸率越小。随着根径的增加,纤维素和半纤维素含量呈增加趋势,木质素含量呈减小趋势。其中火棘木质素含量高于刺鼠李,纤维素含量低于刺鼠李。木质素含量越高,根系极限抗拉力和极限抗拉强度越大,纤维素和半纤维素含量越高,极限延伸率越小。纤维素、半纤维素和木质素在微观的化学结构上韧性和强度可能对根系宏观的力学特性有较大影响。根系在微观结构方面具有与木材一样的微观“多孔结构”,从而对根系产生一定的增韧作用。【结论】根系的木质素、纤维素和半纤维素均对根系的抗拉力学性能有一定影响,在一定程度上揭示了影响根系力学性质内在因素。

【Objective】The aim of this study was to gain an understanding of the relationship between the chemical composition and mechanical properties of roots.【Method】We determined the tensile strength of roots,measured the contents of chemical components,including cellulose,hemicellulose and lignin;and assessed the surface appearance of the roots,with a view toward elucidating the protection mechanism of roots in the soil from a microscopic perspective.【Result】①We found that root diameter had a considerable effect on tensile strength,namely,the larger the root diameter,the higher is the ultimate tensile force,and the smaller are the ultimate tensile strength and ultimate elongation.②The effects of root diameter on chemical composition were consistent with those of mechanical properties,with the contents of cellulose and hemicellulose increasing,whereas that of lignin showed a decrease.Furthermore,we found that whereas the lignin content of Pyracantha fortuneana was higher than that of Rhamnus dumetorum Schneid,the cellulose content showed the opposite pattern.③In terms of toughness and strength,the microscopic chemical structures of cellulose,hemicellulose and lignin had a marked influence on the macroscopic mechanical properties of roots,with a higher lignin content being associated with a greater ultimate tensile strength and tensile resistance,and higher contents of cellulose and hemicellulose being associated with a smaller ultimate elongation.④The surface of roots at the microscopic level was observed to be a“porous structure,”similar to that of the wood,and accordingly is assumed to confer the root system with mechanical strength.【Conclusion】Collectively,our results revealed that inherent factors that influence the mechanical properties of the root to a certain degree provide a theoretical basis for the selection and optimization of tree species for ecological restoration of slope landscapes.