A joint role of iron oxide and temperature for methane production and methanogenic community in paddy soils

Microbial methanogenesis in paddy soils contributes approximately one-fifth of global anthropogenic methane (CH4) release, creating severe negative climate feedback. The dynamics of iron oxides in flooded paddy fields, as well as temperature changes, have an impact on CH4 production. However, the relationship between the two, as well as their interactive mechanisms in influencing CH4 production and microbial communities in paddy soils, is not yet clear. Therefore, we investigated the interactive effects of temperature (15, 25 and 35 °C) and iron oxide (ferrihydrite) on CH4 production and methanogenic community structure in two Chinese paddy soils, one subtropical and one temperate. We characterized shifts in microbial communities using high-throughput sequencing of bacteria, archaea and methanogenic mcrA genes following an anaerobic incubation for 90 days. Our results showed that temperature significantly promoted Fe reduction in paddy soils, and both together regulated CH4 production by reducing the number of methanogens. Additionally, the temperature sensitivity of methanogenesis was higher in the temperate than in the subtropical paddy soil. We also demonstrated that ferrihydrite can inhibit methanogenesis by reducing the relative abundance of Methanosarcinales and altering the community patterns of methanogens in these paddy soils. Likewise, increases in temperature changes the relative abundance of Methanosarcinales and Methanobacteriales, promoting methanogenesis. Overall, our results provide new insights into the role of iron oxides and temperature in regulating greenhouse gas emissions from paddy soils.