Interplay between temperature and redox conditions regulates wetland biogeochemistry and greenhouse gas emissions.

Wetlands play a crucial role in global greenhouse gas (GHG) dynamics, yet their response to climate change is not yet fully understood. Here, we investigate how increasing temperature and oxygen availability interact to regulate wetland GHG emissions through combined analysis of biogeochemical and functional gene measurements. We found distinct temperature-dependent shifts in carbon emission pathways, with CO emissions unexpectedly declining as temperature rose from 15 to 25 °C, while increasing consistently at higher temperatures (25-35 °C), reflecting a transition to more thermally-driven processes. Conversely, CH production exhibited exceptionally high temperature sensitivity in the lower range (Q = 32.3 ± 2.4 in oxic conditions) before normalizing at higher temperatures (Q = 4.1 ± 2.2), suggesting a fundamental shift from aerobic respiration to methanogenesis dominance when temperature increases. Similarly, NO production pathways transitioned from nitrification-dominated at lower temperatures to denitrification-dominated at higher temperatures, supported by substantial changes in ammonia-oxidizing (amoA AOA and amoA AOB) and denitrifying (nirK, nirS, and nosZ) gene expression. We observed unexpectedly high CH production and denitrification activity under oxic conditions, particularly at elevated temperatures, suggesting that anoxic microsites play a crucial role in wetland GHG dynamics. These findings reveal the complex interactions between temperature, oxygen availability and microbial processes in the wetland ecosystem, which underscores the need for incorporating pathway-specific temperature sensitivities into climate models to better predict wetland responses to global change.