植物根系对土壤抗侵蚀能力的影响

EFFECT OF PLANT ROOT SYSTEM ON SOIL ANTI-EROSION

以决定土壤抗侵蚀能力的土壤内在性质为表征指标，以长江中上游几种常见的水土保持林为对象，就植物根系对土壤抗侵蚀能力的影响机制和影响程度进行了研究．结果表明：植物根系能够提高土壤的抗侵蚀能力，且主要通过d≤1mm的须根发挥作用；其可能的机制是：活根提供分泌物，死根提供有机质，作为土壤团粒的胶结剂，配合须根的穿插挤压和缠绕，使土壤中直径d＞7mm、d＝7～5mm和d＝5～3mm3个大粒级水稳性团聚体数量增加，同时既增加了土壤的总孔隙度，又提高了土壤抗冲击分散能力和结构、孔隙的稳定性，从而提高了土壤饱和渗透系数．与无林裸地相比较，林地中表征土壤抗侵蚀能力的土壤各理化性质改善值（Y），与土壤中d≤1mm须根量（Rw）之间服从Y＝a＋bRw的线性关系．本文建立了相应的回归模型，并比较了不同林型根系的作用效果．

Using inherent characteristics of soil which determines soil anti--erosion as indexes, the mechanism and degree of soil anti-erosion by plant root system was investigated with some common forests for water and soil conservation in the upper and middle reaches of the Yangtze River. The resultS indicated that the root system could improve soil anti-erosion by means of fine roots(d≤1mm),and the mechanism might be that the secretion was supplied by living roots and organic matters provided by dead roots served as adhesives,which made the waterstable aggregate of three kinds of particle grades(d>7mm, d =7-5mm, d =5 -3mm)increase in quantity. They could not only increase total porosity of soil, but also improve the anti-disperibility and stability of structure and porosity. Thus,the saturated osmotic coefficient of soil was enhanced. Compared with the soil without plants, the relation between the improving value (y)of physicochemical characteristics for soil which indicated soil anti-erosion and the fine root(d≤1mm)biomass in forest soil obeyed the linear eqution: y=a+bRw. Relevant regression models were established and the effects of root systems in different fored types were compered in this paper.