Project leader: Prof. Dr. Susanne Liebner (GFZ German Research Centre for Geosciences)

In wetlands, microbial CH4 oxidizers (methanotrophs) determine the emission of CH4 to the atmosphere through soil CH4 uptake (SMU). After rewetting of degraded temperate fens, biotic and abiotic drivers on methanotroph community development appear to differ from those in natural wetlands. In the few rewetted temperate fens studied so far, the SMU remained poorly developed even several years post rewetting (Wen et al. 2018). This likely contributed to an overrepresentation of microbial CH4 production relative to microbial CH4 oxidation, an apparent lack of soil CH4 oxidation in situ (Fig A5.1), and consequently high observed CH4 fluxes. Natural drought events, however, appear to stimulate methanotrophic community development. The severe drought in 2018, for example, triggered sustainably lower in situ CH4 fluxes via profound and positive effects on peat methanotrophic diversity and activity (Unger et al., 2021). Thus, soil methanotrophic activity and comunity composition seem to be directly coupled to changes in peatland biogeochemistry. To date, we know only little about the establishment and vulnerability of soil methanotrophic communities and their activity in rewetted temperate fens despite their importance for the GHG budget. Project A5 tackles to fill this gap with the aim to to achieve a predictive understanding on SMU in the heterogeneous landscape of wetscapes 2.0. Poject A5 takes a holistic approach on soil methanotrophic research taking into account spatiotemporal links with biogeochemistry and ecosystem CH4 fluxes, the role of yet poorly constrained methanotrophic taxa, and the vulnerability of soil methanotroph communities post-rewetting. The project specifically investigates soil methanotrophic communities and SMU of rewetted temperate fens in relation to their biotic and abiotic drivers on diverse spatial and temporal scales. It quantifies the role of methanotrophs, including that of anaerobic methanotrophic taxa, in GHG fluxes which is central to projects B1 and S1. A5 realizes its goals through molecular and bioinformatic techniques like -omics and pangenome analysis, through physiological and process studies, and statistical modeling using all experimental levels of WETSCAPES2.0.