Heterogeneity Of Urban Street Tree Size And Its Influencing Factors

Spatial heterogeneity analysis of urban street trees is the basis for optimizing urban forest survey,scientific management and ecological service functions.This study takes two typical cities in Northeast China,Harbin and Shenyang,as an example.Based on the network street view,879 plots of roads and 26,140 trees in Harbin,and 1,339 plots and 40,170 trees in Shenyang,tree height,breast diameter,crown width and crown are determined.The combination of lower-level indicators,semi-variance function and fractal analysis aims to determine the spatial heterogeneity of trees and provide a basis for analyzing the reasonable sampling points of urban forests.It was found that there were significant spatial heterogeneity differences among the different tree-measuring factors in the two cities,which showed significant differences in autocorrelation distances,but there was no obvious directionality(at 0°,45°,90°,135°).The ratio of the semi-variance values in the direction is close to one is isotropic).These spatial heterogeneity are affected by structural and random factors,but the different factors are significantly different.That is to say:the random factor of the canopy size change of Harbin street tree is 26.56%,while the under the branch height,tree height;diameter at breast height,are The proportions were 8.16%,8.14%,and 12.80%,respectively,and the latter were more affected by urbanization-related structural factors(>88%).The base ratios of crown width,crown height,tree height and diameter at breast height of Shenyang city street trees are 13%,11%,11%,and 8%,respectively.It seems that the tree measurement factors of two cities are more affected by structural factors.The measuring factors of tree-measuring factors in Harbin(sequences of canopy size,under the branch height,tree height,diameter at breast height)were 2340 m,1320 m,1470 m,and 1890 m,respectively.The tree-measuring factor of Shenyang City was 3120 m.1980 m,2310 m,2370 m,Considering that the sampling spacing should be controlled within the range to effectively reveal the spatial pattern characteristics,the minimum number of samples that Harbin measures when measuring different indicators is:156 squares of canopy size,440 squares of under the branch height,and 360 tree height.224 squares of diameter at breast height.And 196 squares of canopy size,484 squares of under the branch height,and 361 tree height.361 squares of diameter at breast height in Shenyang;.In the two cities,only the number of breast diameter samples is different,and the other differences are small.While calculating the spatial heterogeneity of urban tree measures,we also use Harbin as an example to analyze its influencing factors.Because of the different tree-measuring factors,the factors affecting spatial heterogeneity will also vary greatly.The influencing factors of tree height heterogeneity are road area ratio,forest vertical structure and LPI;the spatial heterogeneity factors of diameter at breast height are road area ratio,cultivated land area ratio,LPI,LSI;canopy size is forest area ratio The proportion of the number of rings,the proportion of the number of built-up areas,the under the branch height spatial heterogeneity of TA,NP,LSI,ENN-MN,ENN,and PARA are the proportion of impervious area,forest Area ratio,NP,LSI.Some of these influencing factors also have a certain impact on the process.The results of the redundant analysis are also consistent with the results of my correlation analysis.Our research results provide basic data support for urban forest research and management in Harbin and Shenyang,which will help to determine a reasonable sampling plan in the future,and provide a theoretical basis for future urban planning and construction.