Elevated O3 alters soil bacterial and fungal communities and the dynamics of carbon and nitrogen

Abstract Although many studies have reported the negative effects of elevated O 3 on plant physiological characteristics, the influence of elevated O 3 on below-ground processes and soil microbial functioning is less studied. In this study, we examined the effects of elevated O 3 on soil properties, soil microbial biomass, as well as microbial community composition using high-throughput sequencing. Throughout one growing season, one-year old seedlings of two important endemic trees in subtropical China: Taxus chinensis (Pilger) Rehd. var. chinensis , and Machilus ichangensis Rehd. Et Wils, were exposed to charcoal-filtered air (CF as control), 100 nl l −1 (E100) or 150 nl l −1 (E150) O 3 -enriched air, in open top chambers (OTCs). We found that only higher O 3 exposure (E150) significantly decreased soil microbial biomass carbon and nitrogen in M. ichangensis , and the contents of organic matter were significantly decreased by E150 in both tree species. Although both levels of O 3 exposure decreased NO 3 -N in T. chinensis , only E150 increased NO 3 -N in M. ichangensis , and there were no effects of O 3 on NH 4 -N. Moreover, elevated O 3 elicited changes in soil microbial community structure and decreased fungal diversity in both M. ichangensis and T. chinensis . However, even though O 3 exposure reduced bacterial diversity in M. ichangensis , no effect of O 3 exposure on bacterial diversity was detected in soil grown with T. chinensis . Our results showed that elevated O 3 altered the abundance of bacteria and fungi in general, and in particular reduced nitrifiers and increased the relative abundance of some fungal taxa capable of denitrification, which may stimulate N 2 O emissions. Overall, our findings indicate that elevated O 3 not only impacts the soil microbial community structure, but may also exert an influence on the functioning of microbial communities.