计划烧除对云南松林土壤抗剪性能的影响

Effects of Prescribed Burning on Soil Shear Strength in Pinus yunnanensis Forests

[目的]探究计划烧除后云南松林土壤力学特性变化特征,为森林的可持续经营、优化林区计划烧除作业以及防治水土流失提供可靠的科学依据。[方法]以滇中高原云南松林周期性计划烧除样地为研究对象,采用野外调查取样与室内直剪实验相结合的方法,系统研究了计划烧除对云南松林土壤抗剪性能的影响及影响因素。[结果]与未烧除样地相比,计划烧除样地0—20 cm土层中根、细根生物量密度和根长密度显著降低,20—60 cm土层差异不显著。计划烧除后0—20 cm土层抗剪强度、土壤黏聚力显著减小,对深层土壤无显著影响。RDA分析结果表明:计划烧除和未烧除样地均显示土壤抗剪强度指标与土壤有机质、细根根长密度呈显著(p<0.05)正相关关系,细根根长密度在两种处理中均是解释度最高的因子。[结论]周期性计划烧除后细根系分布减少,土壤有机质含量降低,是云南松林地土壤抗剪性能减弱的主要原因。

[Objective]The purpose of this study is to explore the characteristics of soil mechanical properties to prescribed burning in Pinus yunnanensis forests,so as to provide scientific basis for sustainable forest management and optimization of prescribed burning in forest areas and control of soil erosion that may be caused by prescribed burning.[Methods]The sample plots of P.yunnanensis forest in central Yunnan Plateau were selected as the research objects so that to systematically study the effects of prescribed burning on soil shear strength of P.yunnanensis forest by combining field investigation and sampling with indoor experimental analysis.[Results]The root and fine root biomass density and root length density in the 0—20 cm soil layer significantly reduced and the difference in the 20—60 cm soil layer were not significant compared with the unburned forest.The shear strength,soil cohesion significantly reduced in 0—20 cm soil layer after the prescribed burning,the impacts were no significant with the increase of soil depth.The RDA analysis results showed that the soil shear strength,soil cohesion,soil friction angle and soil organic matter and fine root length density significantly positively correlated(p<0.05)in both treatments,and the fine root long density was the highest explaining factor in the two treatments.[Conclusion]The decrease of fine root distribution and soil organic matter content after prescribed burning in Pinus yunnanensis forests are the main reasons for the decrease of soil shear strength.