滇东石漠化坡地浅层裂隙漏失土壤的抗剪强度及其影响因素

Loss Soil Shear Strength and Its Influencing Factors in Shallow Fractures of Rocky Desertification Slopes in Eastern Yunnan Province

[目的]探讨滇东岩溶断陷盆地植被恢复对改善浅层裂隙土壤理化性质及增强土壤抗剪强度的影响,为减缓土壤漏失,有效遏制该区石漠化态势提供科学参考。[方法]通过野外调查取样和室内土壤团聚体湿筛、土壤抗剪试验等方法,分析云南松次生林、小铁仔灌丛裂隙土壤基本性质、土壤抗剪性能的垂直变化特征。[结果]①植被恢复能改善裂隙土壤理化性质,但随着土层深度的变化出现差异。两对比群落裂隙土壤中有机质、砂粒含量、水稳性团聚体(>0.25 mm)随着土层深度的加深呈递减趋势,土壤黏粒含量、水稳性团聚体(<0.25 mm)呈递增趋势;云南松次生林裂隙土壤砂粒(55.46%)、有机质(19.63 g/kg)、水稳性团聚体(76.51%)含量>小铁仔灌丛裂隙(50.16%,11.31 g/kg,67.57%),粉粒(17.55%)、黏粒(26.99%)、小颗粒团聚体(23.49%)含量<小铁仔灌丛裂隙(22.56%,27.27%,31.43%)。②两对比群落裂隙土壤黏聚力都随着土壤黏粒、水稳性细颗粒团聚体的增多而增大(p<0.05),土壤内摩擦角随着砂粒、有机质、水稳性大颗粒团聚体的减少而逐渐减小(p<0.05)。③两对比群落裂隙土壤抗剪强度随土层深度的加深而减小,但云南松群落在提升浅层裂隙土壤抗剪性能上要优于灌丛群落,尤其是在中层和深层裂隙土壤,云南松群落抗剪强度大于小铁仔灌丛,两对比群落裂隙的抗剪强度差异性极显著(p<0.01)。[结论]在滇东断陷盆地石漠化地区,乔林群落更有助于改善中层和深层土壤理化性质,提高土壤抗剪强度,减缓浅层裂隙土壤漏失效应更显著。

[Objective]The influence of vegetation restoration on soil physical and chemical properties of shallow fissures and soil shear strength in karst-faulted basins in Eastern Yunnan Province was explored in order to provide a scientific reference for the mitigation of soil loss and the effective control of rocky desertification in this area.[Methods]The vertical variation characteristics of soil properties and soil shear resistance in the shrub crannies of a secondary forest of Pinus yunnanensis and Myrsine africanan shrub were analyzed by field sampling,indoor wet screening of soil aggregates and soil shear test.[Results]①Vegetation restoration could improve the physical and chemical properties of fractured soil,but there were differences with changes in soil depth.Organic matter,sand content,and water stable aggregates(>0.25 mm)in the fissured soil of two different vegetation communities decreased with increasing soil depth,while the clay content and water stable aggregates(<0.25 mm)increased with soil depth.The contents of sand particles(55.46%),organic matter(19.63 g/kg),and water stable aggregates(>0.25 mm,76.51%)in cracked soil of a secondary forest of P.yunnanensis were more than M.africanan shrub(50.16%,11.31 g/kg,67.57%,respectively).The contents of silt(17.55%),clay(26.99%),and small water stable aggregates(23.49%)were more than M.africanan shrub(22.56%,27.27%,31.43%).②The cohesion of fractured soil in both communities increased with the increaseing water stable aggregates(>0.25 mm)(p<0.05),and the friction angle of soil decreased with decreasing aggregates of sand,organic matter,and water stable aggregates(<0.25 mm)(p<0.05).③The shear strength of the fissured soil in the two communities decreased with increasing soil depth,and the secondary forest of P.yunnanensis community was better than the shrub community in improving the shear strength of the shallow fissured soil,especially in the middle and deep fissured soil.The shear strength of the secondary forest of P.yunnanensis>M.africanan shrub fissure.The difference in shear strength of the fissured soil in the two communities was very significant(p<0.01).[Conclusion]In the rocky desertification region of the fault basin in Eastern Yunnan Province,the arbor community is more helpful in improving the physical and chemical properties of the middle and deep soil,improving soil shear strength,and alleviating the loss of shallow fissured soil.