Temperature Increase in Paddy Soils Remodels the Relationship Between the Anaerobic Food Web and the Q10 of CH₄...

Rice paddies are a major source of anthropogenic CH₄ emissions globally, with the temperature sensitivity (Q10) of CH₄ production playing a key role in forecasting emissions under future climate scenarios. However, the mechanistic links among Q10, the soil microbiome and mean annual temperature (MAT) in paddy soils remain poorly understood. To address this gap, we employed quantitative PCR, amplicon sequencing, genome-resolved metagenomics and metatranscriptomics to investigate CH₄ production dynamics and the response of the methanogenic food web to warming in low MAT (L_MAT, 4°C-9°C) and high MAT (H_MAT, 14°C-16°C) soils. Our results indicate that CH₄ production exhibits a higher Q10 in L_MAT soils, while warming exerts a more pronounced impact on the methanogenic food web in H_MAT soils. Notably, we identified negative correlations between the Q10 and the metagenomic abundance of genes encoding glycoside hydrolases, carbohydrate-binding modules, polysaccharide lyases-related carbohydrate-active enzymes (CAZymes), hydrogenotrophic methanogenesis, and the average genome size (AGS) of the microbiome. Conversely, genes encoding auxiliary activity CAZymes and those associated with acetate metabolism and fermentation were positively correlated with Q10. Genes linked to acetoclastic and hydrogenotrophic methanogenesis exhibited lower responsiveness to warming in L_MAT soils compared to H_MAT soils. Additionally, warming led to a significant reduction in both gene and transcript abundances associated with methylotrophic methanogenesis across both MAT regimes. These findings provide novel insights into the temperature-dependent restructuring of methanogenic pathways and resource utilisation strategies in paddy soils, with important implications for predicting CH₄ emissions under climate change.