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

Purpose: Microbial oxidation by bacteria with the potential to oxidize C1 compounds (methanotrophs) is the only biological sink for atmospheric methane (CH ₄ ). 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. Materials and methods: We collected soils from different vegetation types in one subtropical and one temperate forest in China. Potential CH ₄ oxidation rates and methanotroph communities were assessed via laboratory incubation and pmoA-based phylogenetic analysis, respectively. Results and discussion: Across all sampling sites, we observed distinct variations in methanotroph community composition and CH ₄ oxidation rates. In all soils, CH ₄ oxidation rates increased with increasing CH ₄ concentration. Elevated temperature resulted in an increase in the CH ₄ 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. Conclusions: It is suggested that intrinsic differences in CH ₄ oxidation rate responses to temperature between coniferous and deciduous soils are likely due to different methanotroph community structures. Taken together, the direction of CH ₄ feedback responses to disturbance was site specific.