The Evolution Of Landscape Fragmentation And Construction Of The Ecological Security Pattern In Xishuangbanna

The rapid disappearance of tropical rain forests in the world has led to the destruction of habitats for organisms,and great threats have been posed to the service functions of ecosystems and the protection of biodiversity.Owning the largest existing tropical forest in China,Xishuangbanna is a key area for biodiversity conservation in the international community.However,the process of urbanization and human-land conflicts are responsible for the rapid disappearance of tropical forest and increased fragmentation of regional landscapes,resulting in the degradation of ecosystem services and reduction of biodiversity,which have put tremendous pressure on regional ecological security.The construction and optimization of the ecological security pattern can improve the stability of the ecological environment,restore ecological functions and protect biodiversity.It is an important spatial approach to solving regional ecological environmental problems and improving regional ecological security.Xishuangbanna is taken as an example in this thesis.Landscape classification is conducted based on the landsat data of 1991,2000,2010 and 2019.Optimal scale selection,correlation analysis and spatiotemporal gradient analysis of transects are carried out through moving window analysis method,geostatistical analysis method and landscape software of Fragstats to select 8 landscape fragmentation indexes.A comprehensive fragmentation index was constructed through the entropy weight method to analyze the characteristics of spatiotemporal changes and the spatiotemporal difference.On the basis of the analysis of landscape fragmentation and aiming at the current ecological pattern of Xishuangbanna in 2019,the ecological source is extracted through hot spot analysis based on the ecosystem service functions and ecological sensitivity,construct a comprehensive index of landscape fragmentation to modify the resistance coefficient according to the ecological pattern framework of"source-corridor-node".The circuit theory model is applied to identify ecological corridors and ecological nodes based on so as to optimize and give suggestion to the construction of ecological security pattern in Xishuangbanna area.Major findings are as follows:(1)The landscape fragmentation results from 1991 to 2019 show that 600m is the best spatial scale for the study area,and the correlation among the 8 landscape fragmentation indexes is more than 0.8;the fragmentation index of each landscape extracted with the Lancang River as the transect zone is characterized in that the overall fragmentation of the southwest of the transect zone is greater than that of the northeast,and the fragmentation of river valley dam area is higher than that of mountain area.The overall landscape from 1991 to 2019 is developing towards fragmentation.(2)The analysis of the spatiotemporal changes of the comprehensive fragmentation index shows that the mean values of comprehensive fragmentation index from 1991,2000,2010 to 2019 were 0.15,0.22,0.22 and 0.21 respectively in Xishuangbanna area,which shows a trend from increasing to decreasing.The overall fragmentation of the landscape was mainly slightly fragmented,the highest proportions of slightly fragmented and lightly fragmented landscapes were 1991 and 2019respectively,and the remaining proportion fragmented accounted for the largest number in 2010;the spatial autocorrelation method is employed to analyze the spatial difference of the comprehensive index of landscape fragmentation.Moran'I indexes of landscape fragmentation comprehensive index are 0.521,0.533,0.50 and 0.498,it is a positive global spatial correlation in the analysis of global spatial autocorrelation.In the local spatial autocorrelation analysis,the areas with high fragmentation of landscape in Xishuangbanna are areas with dense human activities,and the spatial distribution is mainly construction land and agricultural planting areas.The areas with low fragmentation are mostly the natural forest land located in nature reserves.(3)20 important ecological source areas are extracted in the construction of ecological security pattern in Xishuangbanna area,covering a total area of 7709.56km~2,and accounting for 40.33%of the study area;compared with the resistance surface corrected by night light data,the spatial differentiation of the landscape resistance surface corrected based on the landscape fragmentation index is more significant;and in the identification of ecological corridors,the spatial distribution of the corridors,the reduction of conflict points of human activities,network connections optimal corridor verification delivered relatively good results.Among them,the potential corridor is 631.73km,and the key corridor is 278.59km;the ecological nodes include 20 resource strategic points,4 ecological strategic points,27 ecological temporary rest points and 24 ecological break points,constructing an ecological security pattern.(4)Optimize spatial elements based on the ecological security pattern of Xishuangbanna area.The ecological space is divided into source protection zone,ecological buffer zone,ecological transition zone,and production development zone,with areas of 7709.56km~2,5804.65km~2,3961.37km~2 and 1638.52km~2 respectively;in the optimization of the ecological source area,the ecological conflict zone are parted on the basis of ecological source;in the optimization of ecological corridors,2 resistance corridors and 22 natural corridors are optimized;finally,the ecological space structure layout of"one belt,one corridor and four groups"was optimized.After evaluating the connectivity,the connectivity index of each landscape has been significantly improved after the construction and optimization of ecological security.