Natural wetlands serve as important global carbon sinks and play a critical role in regulating greenhouse gas emissions. However, the widespread conversion of wetlands into paddy fields has raised concerns, and its impacts on ecosystem net carbon fluxes, as well as the associated soil environmental and microbial regulatory mechanisms, remain insufficiently understood. In this study, natural wetlands and their converted paddy fields in the Tumen River Basin of China were selected to systematically evaluate the effects of land-use change on soil microbial communities and greenhouse gas (CH4 and CO2) fluxes. In natural wetlands, CH4 exhibited net emission, whereas CO2 showed net uptake. After conversion to paddy fields, CH4 remained a net emission but with significantly reduced flux, while CO2 shifted from net uptake to net emission, indicating a fundamental alteration in carbon balance. The conversion from wetlands to paddy fields significantly altered the composition and diversity of methanogenic and methanotrophic communities, accompanied by changes in the contribution of microbial communities to net ecosystem CH4 and CO2 fluxes. This land-use transformation was likely associated with a shift in the regulatory mechanism of net ecosystem carbon fluxes, from a predominantly microbially mediated biotic process toward a regulation pattern more strongly influenced by abiotic factors, particularly external inputs. Overall, the conversion of natural wetlands to paddy fields modifies net ecosystem carbon flux by restructuring the coupling between microbial communities and the soil environment. Based on these findings, management practices such as optimizing irrigation regimes (e.g., intermittent irrigation and mid-season drainage) to regulate soil redox conditions, and rationally controlling nitrogen fertilizer inputs to reduce excessive external nutrient disturbances, can be adopted to adjust the relative role of microorganisms in regulating net ecosystem carbon fluxes.
Chen et al. (2026) studied this question.