Wetland hydrological dynamics and methane emissions

Wetlands are the largest and most uncertain biological source of atmospheric methane, with hydrological fluctuations exacerbating this uncertainty. Here we critically explore the complex relationship between hydrological fluctuations and methane emissions in wetlands by integrating observations from 31 FLUXNET wetland sites with a comprehensive literature review. We present the prevalence and patterns of water table fluctuations and their contribution to uncertainty in methane fluxes. We also highlight key pathways through which these fluctuations affect methane production and emission, such as soil redox heterogeneity, changes in substrate availability and alternative electron acceptor pool, the contribution of different methane transport pathways, and the non-linear responses of community structure and activity of methanogens and methanotrophs to hydrological fluctuations. This review aims to improve the accuracy of wetland methane emission reports by carefully assessing biogeochemical kinetics under hydrological fluctuations. Water table fluctuations in wetlands impact methane production and emissions via biotic and abiotic pathways including soil redox, substrate availability, electron flow, gas transport, and microbial community structure, according to the analysis of observational data from 31 wetland sites and a broad literature review.