Remote Sensing Monitoring Of Vegetation And Its Resilience Based On Critical Slowing Down Model

On a global scale,ecosystems have been disturbed by environmental changes and human activities,and a series of natural disasters such as large-scale drought,fire and soil erosion have occurred frequently.As a key parameter affecting the quality and stability of ecosystem,vegetation restoration has become an important research content.Monitoring the growth state of vegetation under disturbance stress and studying the resilience of vegetation are of great significance for maintaining the stability and sustainable development of the whole ecosystem.In this paper,long-term serial leaf area index(LAI)data,Globe Land30,DEM data,Terra Climate data,geological disaster data,critical slowing down model(CSD)and case model were used to study vegetation resilience in the Three Gorges Reservoir Area(TGRA).After pixel by pixel time series decomposition of LAI,the time autocorrelation index of LAI at time T and T-1(AR(1))was calculated as the index to monitor vegetation resilience in the Three Gorges Reservoir area,and the driving factors of vegetation resilience were analyzed.The accuracy of the critical slowing down model was verified by a case model,and the temporal and spatial distribution characteristics of land use type change,vegetation and vegetation resilience in the Three Gorges Reservoir area were analyzed.The applicability of remote sensing products and the critical slowing down model in vegetation evaluation was discussed.The main research conclusions are as follows:(1)In 2000,arable land and forest were the main types of land use in the Three Gorges Reservoir area,accounting for 88.07% of the total area.Other land use types account for a relatively small proportion.Arable land is mainly distributed in western and central areas.Forests are mainly distributed in the eastern and northern regions,while other land use types are scattered.In 2010,the main land use types in the Three Gorges Reservoir area were cultivated land and forest,accounting for 90.18% of the total area.In 2018,arable land and forest were the main types of land use in the Three Gorges Reservoir area,accounting for 87.76% of the total area.Compared with 2000,the amount of bare land increased by 0.4km~2.Compared with 2010,the area of cultivated land and artificial surface changed significantly in 2018.The area of cultivated land decreased,the area of artificial surface increased,and 0.4 square kilometers of bare land was added.During the 18 years from 2000 to 2018,there was a correlation transformation among land use types,and the area changed by land use types was 4970.78km~2,accounting for 8.50% of the total area of the Three Gorges Reservoir area.The area of forests and water bodies increased significantly;The area of grassland and cultivated land decreased significantly.The vegetation resilience of forest,shrub and grassland is higher than that of wetland.(2)LAI in the northeast and southern parts of the Three Gorges Reservoir Area was higher,while LAI in the central and western parts was lower.The LAI value of Chongqing section was lower,while that of Hubei section was higher.From 2000 to2018,it showed an increasing trend in the south and the north,and a decreasing trend in the west,northeast and some parts of the north.The increase of LAI in Wujiagang district was the most obvious,with a growth rate of 1.02/ year.Shizhu Tujia Autonomous County of Chongqing showed the most obvious decline,with a rate of0.16/ year.(3)The vegetation resilience was higher in the northeast and south of the Three Gorges Reservoir Area,but lower in the central and west.The resilience of forest,shrub land and grassland was strong,but that of wetland was low.Xingshan County,Wuxi County and Yiling District of Yichang City had higher vegetation resilience,while Jiangbei District,Dadukou District and Nanan District of Chongqing had lower vegetation resilience.(4)There is a significant negative correlation between the time autocorrelation index calculated based on the critical slowing down model and the restoring force calculated based on the case model,which indicates that the critical slowing down model has good applicability in monitoring the vegetation restoring force in the Three Gorges Reservoir area.(5)Different driving factors had different effects on vegetation resilience.The change trend of vegetation resilience was positively correlated with precipitation and negatively correlated with temperature.The vegetation restoration force calculated by the critical slowing down model is in good agreement with that calculated by the case model,which indicates that the critical slowing down model has good applicability in the Three Gorges reservoir Area.This paper provides a theoretical basis for ecological management decision-making in the Three Gorges reservoir Area.