Changes in methane oxidation ability and methanotrophic community composition across different climatic zones

Microbial oxidation by bacteria with the potential to oxidize C1 compounds (methanotrophs) is the only biological sink for atmospheric methane (CH4). Aerobic methanotrophs are particularly active in forest soils, but the role of aerobic methanotrophs in native forest soils in China remains poorly understood. The pmoA gene, encoding the key enzyme methane monooxygenase (particulate MMO), is widely used to identify methanotrophic communities. We collected soils from different vegetation types in one subtropical and one temperate forest in China. Potential CH4 oxidation rates and methanotroph communities were assessed via laboratory incubation and pmoA-based phylogenetic analysis, respectively. Across all sampling sites, we observed distinct variations in methanotroph community composition and CH4 oxidation rates. In all soils, CH4 oxidation rates increased with increasing CH4 concentration. Elevated temperature resulted in an increase in the CH4 oxidation rates in coniferous forests, while a decrease in deciduous forests. Restriction fragment length polymorphism analyses indicated that methantrophic community varied in different vegetation types. The methanotroph communities were dominated by type II methanotrophs (including soil cluster alpha (SCα), Methylocystis, and USCα) and type I methanotrophs (including USCγ and Methylobacter) in deciduous and coniferous forests, respectively. It is suggested that intrinsic differences in CH4 oxidation rate responses to temperature between coniferous and deciduous soils are likely due to different methanotroph community structures. Taken together, the direction of CH4 feedback responses to disturbance was site specific.