Climatic control on soil microbial methane uptake across forest biomes

Soil microbial methane (CH₄) uptake is critical for mitigating global warming and is sensitive to climate change. However, how climatic changes regulate the capacity of forest soils to uptake CH₄ across environmental gradients remains largely unclear. Here, we investigated the distribution and key drivers of the CH₄ oxidation potential (MOP) across 26 forests along a latitudinal gradient of 4000 km with structural equation modeling and multiple regression. We found that climate was a fundamental driver of MOP, with soil MOP peaking in the subtropical zone and being the lowest in the temperate zone. Structural equation modeling provided evidence that soil MOP was directly driven by changes in the aridity index and indirectly by regulating plant biomass, followed by soil properties. We also found that the environmental context influenced MOP within particular biomes and vegetation types. For example, the cold temperate zone exhibited a significant positive correlation between soil copper content and MOP, suggesting copper as a key factor explaining the variation in soil MOP in this region, as the particulate methane monooxygenase that catalyzes the oxidation of CH₄ is a copper-bound membrane metalloenzyme. Within coniferous broad-leaved forests, soil manganese emerged as a significant predictor of soil MOP, because CH₄ oxidation could be coupled to the reduction of manganese oxides, highlighting its biome-specific role in ecosystem functioning. In addition, methanotrophic richness was most important for explaining soil MOP in coniferous forests due to the lower alpha diversity of methanotrophs observed here. Our study provides solid evidence that climate and local environmental conditions regulate CH₄ sinks in forest ecosystems, with implications for predicting terrestrial carbon cycling under global climate change.