白龙江流域不同植被类型修复模式下土壤理化性质与边坡稳定性

Physicochemical Properties of Soil under Restoration of Different Vegetation Types and Resulting Slope Stability in the Bailong River Basin,China

植被修复是边坡生态治理的有效手段。目前,植被对边坡稳定性影响的研究侧重在根系的锚固作用,而有关植被对土壤物理化学性质的影响所导致的土体边坡稳定性的变化研究比较少。本研究以白龙江流域滑坡区植被修复林地、灌木-草地、草地与裸地为研究对象,测量了修复14年后不同植被类型下土壤的基本物理化学特性与力学特性,主要分析了粒度、团聚体、土壤矿物等理化性质与抗剪强度的关系,并通过数值模拟软件综合对比了不同植被修复模式下土体的边坡稳定性。得到了以下结果:(1)植被修复可以显著改变土壤的物理化学性质,灌木-草地相对于其他两种修复模式可以明显提升细颗粒(黏粒、粉粒)和粘土矿物的含量,林地对土壤团聚体形成的促进效果最好。(2)土壤的平均重量直径越大,内摩擦角越大,细颗粒的含量与粘聚力呈高度拟合的指数关系(R2=0.99)。粘土矿物含量与土壤粘聚力呈正相关。(3)经过14年的修复,不同植被修复模式下土体的边坡稳定性都得到了一定程度的提升,其中灌木-草地群落对土体边坡稳定性的加强效果最好。极端降雨条件下,边坡稳定性安全系数从大到小依次为灌木-草地(3.20~2.58)、林地(3.03~2.44)、草地(2.91~2.41)、裸地(2.68~2.25)。本研究有助于加强对不同植被类型对土体边坡稳定性的作用机制的认识,也可为该区域植被修复模式提供一定的建议。

Vegetation restoration is an effective means of ecological control of unstable slopes.Although past research elaborated the anchoring effects of vegetation root systems on stabilizing unstable slopes,most studies neglected the influence of vegetation on the physicochemical properties of soil with the subsequent changes in slope stability.In this study,lands including woodland,shrub-grassland,grassland and bare land in a landslide area of the Bailong River basin,Gansu province,China,were selected for examining the changes in fundamental physicochemical and mechanical properties of soils under restoration of different vegetation types after fourteen years of artificial rearing.The relationships between physicochemical properties such as particle size,aggregates,soil minerals and shear resistance were analyzed,and the slope stability of soil bodies under different vegetation restoration was comprehensively compared by numerical simulation software.(1)Vegetation restoration significantly changed the physicochemical properties of soil.The mode of shrub-grassland planting can significantly enhanced the content of fine particles(clay and silt)and clay minerals in slope soil relative to the other two restoration modes of woodland and grassland planting,and the woodland planting had the best effect on promoting the formation of soil macroaggregates.(2)An increase in the mean weight diameter(MWD)of soil resulted in a greater internal friction angle(φ).There was an exponential relationship between fine particle content and soil cohesion(R2=0.99).Furthermore,the clay mineral content fitted a positive correlation with soil cohesion(c).(3)After fourteen years of restoring,the restoration of land with different types of vegetation,led to an improvement in slope stability to a certain extent.Among the different types of vegetation,the shrub-grassland community was found to be the most effective at enhancing soil slope stability.Under extreme rainfall conditions,the factor of safety(FoS)for slope stability was highest in the shrub-grasslands(3.20-2.58),followed by woodlands(3.03-2.44),grasslands(2.91-2.41),and bare lands(2.68-2.25).This study would help to promote the understanding of the mechanism of vegetation planting on slope stability and may also provide suggestions for vegetation restoration model selection in the study area.