Analysis On The Characteristics And Changes Of Vegetation Spatial Network In Jinhua

Networks are collected by nodes and edges.It can use specific indicators to describe its topology features.Spatial network is one type of network,and each element in the network has the characteristics of geographical location.Therefore,when exploring the features of the temporal and spatial changes of a certain element,spatial network theory can show unique advantages.In recent years,the spatial network has been partially applied in the socio-economic field,but there has been very little application in natural geography.This study takes Jinhua as the research object,introduces spatial network analysis method for the first time,considers a single vegetation community as part of the spatial network,and analyzes its structure as a whole.Based on the establishment of the Jinhua vegetation spatial network model,the characteristics of the spatial network of vegetation in 1995 and 2015 in Jinhua City and the impact and mechanism of urbanization on vegetation function were analyzed.In the study,a working program designed for spatial network analysis was designed to be applied to the analysis of planar elements containing position and time information.The nodes and edges will be assigned weight,and the structural characteristics of the vegetation network are described using indicators,and the degree,degree distribution,and local importance of the vegetation network are analyzed.The main findings of this article are as follows:(1)By using sensing images and based on GIS and ENVI technology,the vegetation information of Jinhua City was extracted from the two phases of remote sensing data in 1995 and 2015,and vegetation patch contours were obtained through remote sensing visual interpretation and automatic data extraction methods.The basic geometric characteristics of the obtained vegetation patches were 306 and 265,respectively.In 2015,The patch density,average area decreased,but the total patch perimeter increased.(2)Analyzing and comparing the data from 1995 and 2015,we can see that the degree of vegetation network in Jinhua City was 24.03 and 21.12,respectively,and the degree of centrality declined to decrease.In particular,the number of nodes between 31 and 35 with high centrality in 2015 was significantly lower.In 1995,the center of vegetation distribution gradually moved towards the urban boundary;the density of vegetation network decreased and the stability of the network was relatively low,and this phenomenon was more pronounced in areas with higher population density and lower ground.(3)The numbers of spatial network edges obtained in two years are 3827 and 2799,respectively.The weights of the edges decrease by 7.66%on the edge between[6.08,8.32],but the weights The increase of 9.97%in[1.59,4.48]reflects that the structure of the vegetation network was more stable in 1995,but the original larger vegetation patch area decreased and the radiation level decreased in 2015,but the degree of patch fragmentation increased.(4)Different network forms can be obtained based on different search radius,and comparison shows that different edges will be generated.The larger the search radius,the higher the number of edges,the tie value,the median,and the maximum value.However,as the number of edges with shorter distances increases,the average edge length decreases when the search radius is 10 km.(5)Vegetation is an important part of the natural geographical environment.By reading the literature analysis,vegetation functions can be summed up in three types:natural function,social function,ecological function.In combination with natural and socio-economic conditions and national policy outlines,the county administrative region by Jinhua can be divided into three types according to the functions of vegetation.The multifaceted factors that are dominated by urbanization affect the evolution of the structure of the vegetation network and hinder the development of its inherent functions.The analysis shows that urbanization affects vegetation function by affecting plant growth and quantity,and affecting vegetation community spatial distribution.This study takes Jinhua as the research object,analyzes the layout of vegetation from the perspective of spatial network,and introduces the related theories of ecology and landscape science to analyze the indicators.The study not only shows that the spatial network theory can be introduced into the study of natural geography,but also can provide guide for the construction of ecological civilization in Jinhua City.