Ozone enrichment and drought stress have more negative effects on invasive leguminous woody species than co-occurring native species

Ozone (O3) enrichment and drought stress are common phenomenon of global climate change. However, it remains unknown to what extent these factors might affect leguminous woody plant species invasion. In an open-top chamber (OTC) experiment, we grew four congeneric pairs of invasive and native woody plant species under two levels of O3 concentrations (ambient vs. elevated) and water conditions (dry vs. wet). We studied the effects of O3 enrichment and drought stress on the biomass, biomass allocation and leaf number of these four pairs of invasive vs. native woody species that are common in temperate forests. The results showed that O3 enrichment and drought stress alone reduced the total biomass of invasive woody species significantly greater than those of co-occurring native species. Moreover, O3 enrichment reduced the root biomass allocation of invasive species significantly more than that of native species. Under elevated O3 environments, the ratio of damaged leaves to total leaves for invasive species was 22.6% and 33.9%, and for native species was 13.9% and 24.4%, under dry and wet conditions, respectively. Results suggested that negative effects of O3 enrichment on plants was alle-viated under drought conditions, and such negative effects on invasions of woody plant species were both detected from biomass allocation and visible foliar injury perspectives. Our study demonstrated that elevated O3 and drought stress have stronger adverse effects on invasive woody species than that co-occurring native species. The invasive woody plant species may be facilitated for invasion to the areas with lower O3 concentration or higher precipitation.