Land-use effects on microbial methane dynamics across European peatlands

Peatlands are globally important sources and sinks of methane (CH₄), yet the extent to which land-use change alters the balance between methanogenesis and methane oxidation across peatland types remains poorly constrained. Here, we quantify potential methane production and aerobic methane oxidation across 27 peatland sites within the EU Biodiversa+ project network, spanning Estonia, Finland, Germany, and Czechia and encompassing pristine, drained, and rewetted bogs and fens.

We combined laboratory incubation assays with molecular approaches to assess methane cycling potential in both the aerobic peat layer and below the water table. Potential CH₄ production and oxidation rates were measured under controlled conditions, alongside quantitative PCR targeting methanogenic (mcrA), methanotrophic (pmoA), and total bacterial (16S rRNA) genes. Shotgun metagenomics and 16S rRNA gene sequencing were used to explore the genomic potential for methane oxidation and to identify microbial taxa involved.

Preliminary results indicate that pristine peatlands exhibit the highest potential rates of both methane production and oxidation. Drained sites show strongly reduced methanogenic potential, while rewetted sites display partial recovery, with rates generally remaining lower than in pristine systems. Higher methane oxidation rates in long-term rewetted sites (>15 years) suggest that functional recovery may increase with time since rewetting. When separated by peatland type, bogs show higher methane cycling potentials than fens across all land-use categories.

Pristine peatlands consistently showed highest methanogen gene abundances compared to rewetted and drained, particularly in the anaerobic peat layer. Methanotrophic gene abundances were highest in pristine peatlands in the aerobic layer; however, anaerobic layers of rewetted and drained peatlands harbored higher methanotrophic communities than in their aerobic layers. This suggests that methanotrophic communities in managed peatlands may establish deeper in the peat profile, potentially in response to oxygenic microsites or dynamic redox conditions. In rewetted and drained sites, pmoA gene abundance explained ~20% of the variation in methane oxidation rates, and mcrA explained ~10% in rewetted sites.

Overall, these findings suggest that drainage substantially suppresses methanogenic potential, while rewetting promotes partial functional recovery, particularly in bog systems and on timescales of at least decades. Integrating process-based and molecular data provides new insight into how land-use change shapes peatland methane cycling.