Carbon availability and microbial activity manipulate the temperature sensitivity of anaerobic degradation in a paddy...

Soil contains a substantial amount of organic carbon, and its feedback to global warming has garnered widespread attention due to its potential to modulate atmospheric carbon (C) storage. Temperature sensitivity (Q₁₀) has been widely utilized as a measure of the temperature-induced enhancement in soil organic carbon (SOC) decomposition. It is currently rare to incorporate Q₁₀ of CO₂ and CH₄ into the study of waterlogged soil profiles and explore the possibility of artificially reducing Q₁₀ in rice fields. To investigate the key drivers of Q₁₀, we collected 0-1 m paddy soil profiles, and stratified the soil for submerged anaerobic incubation. The relationship between SOC availability, microbial activity, and the Q₁₀ of CO₂ and CH₄ emissions was examined. Our findings indicate that as the soil layer deepens, soil C availability and microbial activity declined, and the Q₁₀ of anaerobic degradation increased. Warming increased C availability and microbial activity, accompanied by weakened temperature sensitivity. The Q₁₀ of CO₂ correlated strongly with soil resistant C components, while the Q₁₀ of CH₄ was significantly influenced by labile substrates. The temperature sensitivity of CH₄ (Q₁₀ = 3.99) was higher than CO₂ emissions (Q₁₀ = 1.78), indicating the need for greater attention of CH₄ in predicting warming's impact on anaerobic degradation in rice fields. Comprehensively assessing CO₂ and CH₄ emissions, the 20-40 cm subsurface soil is the most temperature-sensitive. Despite being a high-risk area for C loss and CH₄ emissions, management of this soil layer in agriculture has the potential to reduce the threat of global warming. This study underscores the importance of subsurface soil in paddy fields, advocating greater attention in scientific simulations and predictions of climate change.