Ecological Restoration Evaluation Of The Sparkling Lake Dam In Jiuzhai Valley Based On Vegetation-soil-soil Fauna System

On August 8,2017,an earthquake of magnitude 7（on the Richter scale）occurred in Jiuzhaigou County,the epicenter was located in the Jiuzhai Valley Natural Scenic Area.The natural heritage site suffered serious damage,including the Sparkling Lake travercaf dam burst,forming a breach 40-meter long,12-meter wide and 15-meter deep,and the 45×104m³water landscape completely disappeared.The research group completed the landscape restoration of the damaged dam and the landscape conservation of the surrounding area,and realized that the restored Sparkling Lake presented a great landscape visual effect.However,the long-term stability of the landscape depends on landscape ecological processes.This study takes The Sparkling Lake restored dam and its surrounding areas as the research object,and divides it into repaired dam（artificial restoration）and original dam（natural restoration）according to methods of vegetation restoration.In consideration of vegetation,soil-fauna and soil ecological process,analyzing the dynamic characteristics of landscape ecological process of the Sparkling Lake dam after restoration.The main research results are as follows:（1）In terms of vegetation composition,within a short time after restoration,the number of herb species in the repaired dam area was significantly higher than that in the original dam area,and the herb species composition was significantly different.The number of shrub species in the repaired dam was little different from that in the original dam,but there was a great difference in the species and the number of plant individuals.With the increase of restoration years,the species number,individual number and biodiversity index of herbs and shrubs in different regions gradually approached,and the similarity gradually increased,while the difference of vegetation composition decreased year by year.（2）In terms of soil physicochemical properties:within a short time after restoration,there are great differences and changes in soil characteristics between the repaired dam and the original dam,specifically,soil p H,extracellular enzyme activity,soil carbon and nitrogen content are significantly different.With the increase of restoration years,soil extracellular enzyme activity,soil carbon and nitrogen content increased to varying degrees,and the differences in soil characteristics between different regions gradually decreased.Meanwhile,the seasons had certain influence on the soil ecological process in the study area.（3）In terms of soil-fauna composition,there are significant differences in the number of species and individual of soil-fauna between the repaired dam and the original dam.In the early stage after ecological restoration,with the increase of restoration year,the number of soil-fauna individual in the study area increased significantly,and the diversity index of soil-fauna community in different areas decreased significantly,while the similarity showed an increasing trend.（4）The results of correlation analysis showed that the number of species and individual of soil-fauna were significantly positively correlated with the number of herb in the early stage after restoration,and were significantly positively correlated with soil physicochemical indexes（p H,NAG activity,NH₄⁺-N content,NO₃^--N content,DOC,DON,MBC,MBN and TOC）in summer.The correlation between soil-fauna community structure and soil physicochemical characteristics was not obvious in winter.In the study,the dominant groups of soil-fauna showed different correlations with plant composition and soil physicochemical properties in different seasons.With the increase of restoration year,the number of dominant groups of soil-fauna in the study area increased to varying degreesIn conclusion,the results of this study confirm that the changes of soil-fauna community in the restored dam area of the Sparkling Lake are closely related to vegetation and soil nutrient cycling.The structure of soil-fauna community,soil characteristics and vegetation composition can reflect the changes of landscape ecological process together,and can be used for scientific assessment of ecological restoration effectiveness.As for the restored dam of the sparkling Lake,the differences in vegetation composition,soil ecological process and soil-fauna community structure decrease yearly with the increase of restoration-time.It means that the restoration area is gradually integrated into the surrounding natural environment.