Statistical analysis
The index used in this paper are per kilometer benefit (PKB, $/km) and average tree benefit (ATB, $/tree), which indicate the ability of street trees assemblage and individual street tree for ecosystem services provision in a specified area respectively. We used PKB instead of the whole ecosystem services value of a specified area, because the lengths of different areas are various and the PKB would be more comparable.
First, we utilized Grouping Analysis (spatial constraints setting is NO_SPATIAL_CONSTRAINT, and distance method is EUCLIDEAN) in ARCGIS to categorize the subdistricts for the value of PKB and ATB into 3 categories respectively. Second, we categorized the subdistricts according to the factors we assumed to have effects on the distribution of ecosystem services provided by street trees assemblage (population density, city sprawl and public policy) and do the statistical analysis in Excel.