松属、青冈属乔木侧根的强度在防护林固土护坡作用中的意义

 乔木根系的土壤加强作用是防护林稳定土壤和保护坡面的最有效的机械途径，其中侧根的牵引效应在林地的固土护坡过程中具有重要作用，其潜能与侧根的抗张强度呈正相关关系。本研究构建了侧根抗张强度与其牵引效应的数学模型，对云南山地以云南松林和滇青冈林为代表的松属和青冈属乔木群落进行了分析。结果表明：青冈属和松属乔木侧根的抗张强度分别在40一10MPa和30～5 MPa范围内，量值的高低随侧根直径的增加而降低。两种乔木的侧根在0～60cm的土壤深处有较高的分布密度，由于具有一定的强度，通过它们的牵引效应，侧根使这一深度的根际土层的抗张强度提高了6.85～12.41 kPa。在各个土层，青冈属乔木固土护坡能力明显高于松属，说明松属侧根在浅层土体加固方面具有局限性。

TENSILE STRENGTH IN LATERAL ROOTS OF PINUS AND CYCLOBALANOPSIS AND ITS SIGNIFICANCE IN MAINTAINING SLOPE STABILITY IN A SHELTER-FOREST SYSTEM

Reinforcement by tree roots is the most effective mechanical process effecting soil stability and slope protection in shelter-forests. In mountainous areas particularly, traction of lateral roots plays an important role in this regard. The importance of this effect rises positively with the roots' tensile strength. This study developed a mechanical model of the relationship between the tensile strength and the traction effect of roots. The model was tested in a Pinus-Cyclobalanopsis forest. The results show that the tensile strength of the Pinus and Cyclobalanopsis roots were 30-5 MPa and 40-10 MPa respectively, and increased negatively with root diameter. In the 0-60 cm layer, the density of lateral roots of the two tree species was relatively high and the roots are able to increase the tensile strength of the rooted soil by 6.85-12.41 kPa, through their traction effect. Though the strength of the pine's roots and its role in increasing strength of the rooted soil are significant, the root strength of the Pinus is lower than that of Cyclobalanopsis and other broad leaved trees.