**3. Species composition of Beijing City**

A total of 536 species of plants belonging to 319 genera and 103 families were investigated in the built-up area of Beijing.

From the perspective of family composition, among the 103 families, Compositae is the family with the largest number of species, including 56 species, followed by Rosaceae with 46 species, Gramineae and Leguminosae with 39 and 37 species, respectively. More than 89% of the families contain less than 10 species, and families with less than 5 species account for 69.9%, including 40 families with 1 species. There are 32 families including 2~4 species, and only 11 families including more than 10 species.

In terms of genus composition, among the 319 genera surveyed, *Prunus* and *Artemisia* contain more than 10 species, *Populus, Polygonum*, and *Chenopodium* contain more than 5 species, while 314 genera such as *Rosa*, *Salix*, *Dendranthema* contained less than 5 species, accounting for 98% of the total, of which 217 genera contain only 1 species, accounting for 68% of the total genera, 91 genera with 2~4 species, accounting for 28.5% of the total genera, and 11 genera with more than 5 species, accounting for only 3.5% of the total genera.

In terms of frequency, *Sophora japonica* has the highest frequency of arbors in all quadrats of urban green space plants in Beijing, up to 0.59, followed by *Sabina chinensis*, which is 0.32. *Buxus megistophylla* had the highest frequency of shrub occurrence, which is 0.46, and *Punica granatum* was 0.06. *Setaria viridis*, the most common herb, is 0.2, followed by *Viola philippica*, which was 0.19.
