Soil aeration rather than methanotrophic community drives methane uptake under drought in a subtropical forest.

Little information is available about the effects of drought on soil methane (CH4) uptake and the underlying feedback of the soil microbial community in forest biomes. More importantly, a meta-analysis of the current literature on this topic revealed that there are virtually no data available in subtropical forests. To fill the abovementioned knowledge gap, we carried out a 3-year investigation of in situ CH4 efflux under drought in a subtropical forest, and found that drought significantly increased soil CH4 uptake (P < 0.001). However, drought did not change oxidation potentials and abundances of methanotrophs, and similar methanotrophic communities were observed between the drought and ambient control sites based on metagenomic sequencing analysis. Active methanotrophic communities were dominated by the genus Methylosinus based on DNA stable-isotope probing analysis. Structural equation model analysis indicated that direct drought-derived pathway, i.e., increasing soil aerations, outweighs the indirect pathway, i.e., altering methanotrophic communities and activities, and plays a predominant role in driving soil CH4 uptake in forest ecosystems. To our knowledge, our work is the first study to investigate the effects of drought on in situ CH4 efflux and the underlying microbial mechanisms in subtropical forests.