Abstract: Cities are the primary distribution areas of most invasive plant species and the important starting point of invasion for many invasive plant species. As one of the important issues in urban ecosystems, the composition of urban invasive plant species and their impacts on plant diversity have received increasing attention. With the built-up area of Shenzhen as a case study, we analyzed the species composition of urban invasive plants and their impact on plant diversity using data from 600 urban plant plots (100 m × 100 m). A total of 214 invasive plant species in 55 families and 153 genera were investigated, with herbaceous plants as the leading life type. Tree species Leucaena leucocephala, shrub species Lantana camara and Mimosa bimucronata, and herb species Mimosa bimucronata, Mimosa bimucronata, and Mikania micrantha were the most widespread invasive species. For herb quadrats with different invasive levels, Simpson dominance index, Shannon diversity index, Margalef richness index, and Pielou evenness index all exhibited the same order as severe invasion < moderate invasion < mild invasion. This study revealed the significant effect of mild invasion on urban herb diversity and the evident pattern of herb diversity decreasing trend with increasing invasion level. Our results and methods provide a reference for studying urban invasive plants and preventing urban alien plant invasions.

Key words: urban vegetation, invasive level, TWINSPAN, species diversity