Effects of elevated ground-level ozone on paddy soil bacterial community and assembly mechanisms across four years.

It is well known that elevated ground-level ozone (eO) poses a threat to the ecosystem. Little knowledge about the underground variables, especially on soil microorganisms, however, has been revealed. Such knowledge will tremendously help to advance our understanding of the correlation between ecosystems and climate change, as well as our ability to predict future trajectory. For this purpose, we have collected soil DNA samples (eO vs. Ambient, each having 36 samples) over four years. Our results have verified the temporal responses and the underlying assembly mechanisms of the paddy bacterial community to eO. Contrary to the widespread consensus, it was found that eO stimulated bacterial alpha diversities. The higher complexity and the centralization of the co-occurrence network of the bacterial community suggested that this stimulation was due to a microbial survival strategy in response to the limited resources, which led to the instability of the community. Furthermore, the observed slower temporal turnover of the bacterial community composition in response to eO was due to the decreased deterministic processes derived from plants, which implied that eO disrupted the coordination between soil microorganisms and rice crop. All above phenomena provided novel insights into the adverse influences of eO on the soil microbial community. If O concentration increases continuously, the adverse effects will be aggravated and harm the related ecological functions.