Warm-temperate, immense, and sprawling: plant diversity drivers in urban Beijing, China

Urbanization is one of the most environmentally damaging of human activities, producing large alterations in ecosystem structure, function, species composition and interactions. In this study, we performed a systematic investigation of the plant species richness and density in the city of Beijing, China. We also assessed which socio-economic factors have most influence on plant diversity. Within the city, we found 551 plant species of 313 genera and 103 families, of which 118 were trees, 99 shrubs, and 296 herbs. Nearly half (48.3 %) of the total plant species were aliens. Species richness and density were positively correlated both for tree/shrub and herb taxa, which indicate that although some species predominate in our study area, there is an important array of species in relation to their densities. As expected, most of the socio-economic variables studied showed to be related to at least one of the four plant diversity variables (i.e., herb richness, herb density, tree/shrub richness, and tree/shrub density). Land-use showed a significant relationship in all four cases, which generally had lower values in cultural and education areas (areas that in Beijing are generally characterized by large extensions of urbanized land). The year of establishment was also largely related to plant diversity, with higher values for recently developed areas. This was an expected result given the dynamics of the urban development of Beijing during the last 60 years, which consisted of intense urban sprawling, followed by more environmentally-friendly urbanization practices during the 2000s related to the greening of the city for the olympic games. This dynamics also explained the negative relationship found between the distance to the city center and both tree/shrub species richness and density.