Warming increases CH4 emissions from rice paddies through shifts in methanogenic and methanotrophic communities

Abstract

Warming often stimulates methane (CH₄) emissions from rice paddies, one of the largest anthropogenic sources of CH₄ emissions. However, the responses of methanogenic and methanotrophic communities to warming, particularly within active communities, remain unclear. Therefore, based on a field warming experiment in a rice-wheat system, we investigated the effects of warming on methanogenic and methanotrophic communities, using the DNA stable-isotope probing technology. Our results indicated that warming increased CH₄ emissions by 27–49% over two rice growing seasons compared to ambient conditions. Warming significantly increased the abundance of methanogens by 53%, whereas did not affect activities of methanogens and active methanogenic community. Conversely, warming did not influence the abundance of methanotrophs, but reduced activities of methanotrophs by 44%. Notably, warming led to a significant rise in the relative abundance of the active type II methanotrophic community, which exhibits lower CH₄ oxidation efficiency. These findings suggest that the observed increase in CH₄ emissions under warming conditions is primarily driven by the enhanced abundance of methanogens and the increased presence of less efficient active type II methanotrophs. This study underscores the critical role of active microbial communities in understanding and managing CH₄ emissions from rice paddies in a warming world.