The effects of elevated ozone and CO_(2) on growth and defense of native,exotic and invader trees

Aims Elevated ozone and CO_(2) can differentially affect the performance of plant species.Variation among native,exotic and invader spe-cies in their growth and defense responses to CO_(2) and ozone may shape CO_(2) and ozone effects on invasions,perhaps in part also due to variation between native and invasive populations of invaders.Methods We manipulated ozone(control or 100 ppb)and CO_(2)(ambient or 800 ppm)in a factorial greenhouse experiment in replicated cham-bers.We investigated growth and defense(tannins)of seedlings of Triadica sebifera from invasive(USA)and native(China)populations and pairs of US and China tree species within three genera(Celtis,Liquidambar and Platanus).Important Findings Overall,ozone reduced growth in ambient CO_(2) but elevated CO_(2) limited this effect.T.sebifera plants from invasive populations had higher growth than those from native populations in control con-ditions or the combination of elevated CO_(2) and ozone in which invasive populations had greater increases in growth.Their perfor-mances were similar in elevated CO_(2) because native populations were more responsive and their performances were similar with elevated ozone because invasive populations were more suscep-tible.Compared to other species,T.sebifera had high growth rates but low levels of tannin production that were insensitive to vari-ation in CO_(2) or ozone.Both China and US Platanus plants reduced tannins with increased CO_(2) and/or ozone and US Liquidambar plants increased tannins with the combination of elevated CO_(2) and ozone.The growth results suggest that intraspecific variation in T.sebifera will reduce the effects of CO_(2) or ozone alone on inva-sions but increase their combined effects.The tannin results suggest that defense responses to CO_(2) and ozone will be variable across native and exotic species.The effects of CO_(2) and ozone on growth and defense of native and exotic species indicate that the benefit or harm to species from these global change drivers is an idiosyncratic combination of species origin and genus.