Aerenchyma in emergent plants and rhizospheric microbial communities promote methane fluxes in wetlands

Wetlands are the largest natural source of CH₄ globally, yet our understanding of how environmental parameters and microorganisms affect the production and emission of CH₄ in emergent plant–sediment systems remains limited. In this study, CH₄ fluxes were investigated in a wetland with Canna indica for 42 d, as well as nutrients and microbial community. It was found that the chimney effect formed by aerenchyma in roots, stems, and leaves of C. indica promoted the emission and oxidation of CH₄ in the wetland and reduced the CH₄ concentration in sediments. Canna indica reduced the nutrient release from surface sediments into the overlying water. Pearson correlation analysis showed that temperature, pH, and oxidation–reduction potential were the main influencing factors for CH₄ production and oxidation in the wetland. Canna indica inhibited the diversity of archaeal community but promoted the diversity of bacterial community in the rhizosphere. Stochastic processes had a greater impact on bacterial and archaeal succession trajectories in wetland sediments. Network analysis showed that C. indica promoted interactions among bacteria and archaea that enhanced their ability to resist environmental interference. The well-developed aerenchyma of C. indica provided an important passage for the transport of CH₄ from sediments to the atmosphere and shaped the microbial community structure in the rhizosphere. Meanwhile, CH₄ emissions were also constrained by several variables, such as temperature and physiological adaptation in the long term. Thus, it is necessary to plant emergent plants in areas with low CH₄ emissions and optimize plant configuration in the context of global warming.