Abstract:
Spatial heterogeneity analysis of urban street trees is the basis for optimizing the surveying method and scientificmanagementandimproving the ecological service of urban forest. In order to provide basis for analyzing of reasonable sampling sites of urban forest, the internet street view picture-based remote measurements were used to determine canopy sizeCS(average width),under branch heightUBH, tree heightTH and diameter at breast heightDBH in a total of 879 plots(26 140 trees), combining with the semivariogram analysis and fractal analysis, to characterize the spatial heterogeneity of urban treesin Harbin. By anisotropy analysis,the insignificant differences in the spatial heterogeneity of CS, UBH, TH, DBH in Harbin city were found at 0°, 45°, 90°,amd 135° directions. As shown by the Nugget/base ratio, random effects accounted for 26.56% of spatial heterogeneity of CS, while much less random effects were responsible for the spatial heterogeneity of UBH, TH, DBH(8.16%, 8.14%, and 12.80% of the total heterogeneity, respectively). Thus, the results suggested that the spatial variations of UBH, TH and DBH were likely to be mainly due to the urbanization-related structural factors(such as urban planning etc.) (>88%). The results indicated that spatial heterogeneityof urban tree varied with different tree size parameters, showing significant difference by the self-correlation length(semi-variogram range), i. e. the semi-variogram range values for CS, UBH, TH, DBH were 2 340, 1 320, 1 470 and 1 890 m, respectively. For precisely identifying thespatial heterogeneity of tree size, sampling interval should be within the semi-variogram range. Our data showed the minimum sampling numbers for measuring the targeted indicators are 156 plots for the CS, 440 plots for the UBH, 360 plots for the TH and 224 plots for the DBH. Fractal analysis showed that the fractal values(D value) of CS, UBH, TH, DBH were 1.957, 1.961, 1.961 and 1.971, respectively. The similar fractal values of the targeted indicators, which were close to 2, could suggest that that their spatial variations were mainly observed in smaller scales between neighboring plots(distance:666m). The results of this study provide basic data to support the further research and scientific management ofthe urban forest in Harbin City, as well as to determine reasonable sampling plans in the future study.