Impacts of tropospheric ozone on grassland soil bacterial diversity and function.

Tropospheric ozone reduces plant productivity and can alter species composition in semi-natural ecosystems, but little is known about the potential impact on soil microbial communities and the below-ground processes they govern. Given the consensus that background ozone concentrations are likely to continue rising in the Northern Hemisphere, this study aimed at characterizing the bacterial community and metabolic activity of three grassland soils following nine years’ exposure to controlled levels of ozone. We show that elevated ozone has a small but significant effect on the relative abundance of selected members of the soil bacterial community (specifically members of Acidobacteria, Chloroflexi, Proteobacteria, Actinobacteria, and Bacteroidetes). Furthermore, this shift in community varied with soil type. Although no major shifts in soil carbon substrate-induced respiration or bacterial diversity in response to elevated ozone were observed (at higher taxonomic levels), the changes in relative abundance of some potential keystone species e.g. N fixers, should be especially noted.