Study On The Vegetation Restoration And Soil Physical Properties Of Xiejiadianzi Landslide

After the Wenchuan earthquake in 2008,a strong landslide occurred in Xiejiadianzi.The bad soil condition on the landslide slope made it difficult for plants to survive.After several years of natural restoration,the vegetation on the landslide body gradually enriched,and the soil structure gradually improved.This paper took the effects of plant communities on soil properties during vegetation restoration as a breakthrough point to research vegetation restoration situation,soil physical properties and the relationship between the two.Establish evaluation index system of of soil anti erodibility to evalue soil anti erodibility ability in different altitude position.The main results are as follows:(1)In 2016,the restoration of the vegetation in the landslide was good.arborshrub-grass community structure has formed in all sample plots,and the vegetation type is also very rich.On the whole,with the decrease of the altitude,recovery time incresed,4 α diversity indexes of the community were all decreased,which indicated that the aggregation of single species in the community was enhanced,and the dominant species was also enhanced.The Cody index of different sites was significantly lower than that in 2012 andf 2014,indicating that the rate of species change became more stable at different altitudes.As a whole,a arbor-shrub-grass community structure of lnus cremastogyne-Hydrangea davidii+ Rubu sparkeri-Selaginella nipponica+ Microlepia marginata has been formed on the landslide.(2)Soil bulk density on Xiejiadianzi landslide decreased gradually with the decreasing altitude.The soil porosity and water holding capacity showed a tendency to increase with the decrease of altitude,which indicated that compared with the upper part of the slope,the lower part of the slope had better aeration and water permeability,and the water holding capacity was also significantly improved.All sample plots were light gravel soil,Soil texture with relatively dense.With the altitude drop,gravel and sand content decreased,while the silt and clay content increased,dense soil texture situation gradually improved.The total amount of >0.25 mm aggregates in all plots was lower than 50%,the soil structure was poor,but with the increase of altitude,the total amount increased,which indicated that the soil structure was improved.The ratio of structure deteriorative and MWD(dry)-MWD(wet)decreased with the decrease of altitude,which indicated that the soil structural stability was gradually enhanced.With the decrease of the altitude,the initial infiltration rate,the steady infiltration rate,the average permeability and the infiltration amount have increased.Based on these four characteristics,the evaluation formula of soil permeability was obtained,and it was found that the soil permeability of landslide increased with the decrease of altitude.(3)After correlation analysis,it was found that tree species and shrub species,the total number of trees and the total number of shrubs showed negative correlation.The correlation between Margalef index and other indices was not good in community diversity,but the correlation between Simpson and Shannon-Weiner was significant.The sand content decreasing most helped to reduce soil bulk density.Soil porosity most influenced by particle and clay.Compared with >0.5mm water-stable aggregate,the content of >0.25 mm water-stable aggregate in soil is more favorable to enhance soil permeability.However,the influence of clay content and total porosity on soil infiltration was the largest.The number of tree species and the total number of individuals were helpful to improve soil physical properties.Margalef index showed a negative correlation with most of the soil physical properties,such as soil water holding capacity,soil infiltration.The results indicated that the decrease of vegetation richness on the landslide was beneficial to the improvement of soil physical properties.(4)Select 6 classes 21 indicators as xiejiadianzi soil erodibility factor evaluation system to carry on a soil anti-erodibility evaluation.The results show that the landslide erosion resistance of soil is mainly affected by the soil permeability and porosity and soil anti-erodibility ability decreases with altitude.It indicates that with the recovery time of growth,soil erosion resistance will be increased accordingly.The reason may lie in the accumulation of more organic matter and humus in the soil,thus improving the soil structure.