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