Recovery of methane turnover and the associated microbial communities in restored cutover peatlands is strongly linked with increasing Sphagnum abundance

Vegetation succession is known to affect carbon-cycling patterns of recovering cutover peatlands, displayed as shifts in emissions of the greenhouse gases CO2 and CH4. However, the related plant-microbe interactions are still poorly understood. We aimed to link the recovery of the organisms responsible for CH4 turnover, the methanogens and the methanotrophs, to the re-vegetation related compositional changes of three functional plant types (Sphagna, sedges and shrubs). In peat layers, the Sphagnum coverage was the most influential factor for the activity, abundance and community structures of both these microbial groups, demonstrating a succession pattern towards a pristine stage. Analysis of mcrA and pmoA genes revealed Methanoregulaceae and Methylocystis as the most dominant methanogens and methanotrophs, respectively. The relatively fast recovery of both CH4 production and oxidation in the peat layers supports earlier flux based results from these same fen-type peatland sites. In contrast to peat, CH4 oxidation in living Sphagnum mosses appeared to be independent of vegetation succession as CH4 oMdation potential was similar throughout the succession stages. This indicated that Sphagnum may be a valuable CH4 biofilter especially in the early re-vegetation stages when the oxidation in the peat has not yet recovered. Therefore, we recommend Sphagnum transplantation as a tool for climate friendly peatland restoration with faster recovery of the carbon sink ftmction and altered CH4 emissions.