贡嘎山森林生态系统根系固土力学机制研究

为探索森林生态系统树木根系固土力学机制,对长江上游贡嘎山森林生态系统不同演替阶段主要树种进行了根系抗拉试验.结果表明:各树种根系在受拉情况下,峨眉冷杉(Abies fabri)、冬瓜杨(Populus purdomii)根系为典型的弹性断裂,而杜鹃根系为脆性断裂. 但各树种根系在断裂或完全拔出之前,根系变形量、最大形变率依次均为冬瓜杨＞杜鹃＞峨眉冷杉. 由于各树种根系形态特性及生物学的特性,在弹性形变范围内根系的弹性模量并不是一个常量,随根径的增加而增加. 根系的抗拉强度与根表面积、根径成正相关,即随着树木年龄的增长,其固持土壤的能力也不断增强. 由于冬瓜杨、杜鹃根系的抗拉阻力较峨眉冷杉强,该地区处于演替初期和中期的冬瓜杨、杜鹃和峨眉冷杉等树种形成的混交林的水土保持功能优于演替顶极群落的峨眉冷杉成过熟林.

Mechanisms of soil-reinforcement by roots in forest ecological systems in Gongga Mountain

The mechanisms of soil reinforcement by roots have been researched through the tests for the pull resistance of roots of main tree species which are in the different succession stages of forestry systems on the Gongga Mountain in the upper reaches of the Yangtze River. Results show that ruptures of both Abies fabri and Populus purdomii roots were in standard elastic form but rupture of root Rhododendron spp. was in brittleness form when the roots were pulled. Before the roots were pulled out or ruptured entirely, both amounts of deformation and ratio of the most deformation in different tree roots were in follow order: Populus purdomii>Rhododendron spp.> Abies fabri . Due to different shapes and biological properties of different tree roots, the elastic modulus is not a constant which varies with diameter of roots. The intensity of root pull resistances of roots increases with surface area,and diameter of root. Function of soil reinforcement by roots are enhanced with trees growing up. Functions of soil reinforcement by roots of Populus purdomii and Rhododendron spp. are better than that of Abies fabri ; function for soil erosion control of mixed forest which was in initial succession and metaphase succession and consisted of Populus purdomii, Rhododendron spp. and Abies fabri is better than that of pure Abies fabri forest which was in climax community and was mature or overmature forest.