Urbanization and greenspace effect on plant biodiversity variations in Beijing, China

It is of great significance to understand how urbanization and greenspace areas gradient affect urban plant biodiversity for urban renewal and planning toward urban biodiversity conservation. However, the factors affecting plant diversity under rapid urbanization remain unknown in many cities. To this end,702 vegetation sampling plots from 219 2 km x 2 km grids were selected to explore the urban plant biodiversity variation within two perpendicular 10 km width transects running across the urban center in north-south and east-west directions within the 6th ring road in Beijing, China. Impervious surface area (ISA) and Greenspace area (GSA) of each grid were interpreted from high resolution remote sensing images. ISA mainly includes road surface, asphalt, and buildings, and GSA includes tree, shrub and herb canopy. A total of 396 plant species were recorded, including 95 tree species, 87 shrub species, and 214 herb species. The 396 species belonged to 298 genus and 93 families. We found that woody plant diversity, tree size attributes (DBH, height, canopy breadth), and total plant taxa increased significantly with increased urbanization while herb plant diversity decreased significantly. However, the GSA has no significant impact on plant diversity and taxa. We further found the higher woody plant diversity and lower herb plant diversity in ISA's with a percentage > 50%, and in the ISA percentage < 50% with larger ISA and GSA area (ISA+GSA percentages (i.e., >80%). ISA and GSA can thus be predictive factors for estimating urban plant diversity, which was related to urban planning and different greening decision-makers. The results of this study have important implications for further understanding how current urbanization factors affect plant diversity, which could implement better scientific urban planning to conserve and restore urban biodiversity in many cities around the world.