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Peatlands, covering just three percent of the Earth's land, store nearly one-third of the world's soil carbon. Over thousands of years, their waterlogged conditions have slowed decomposition, a process where organic material like dead plants breaks down, mostly due to microorganisms. However, draining peatlands for farming and infrastructure disrupts this balance, turning them into significant sources of greenhouse gases. Drained peatlands contribute four to six percent of global COâ‚‚ emissions annually and also experience gradual sinking, increasing flood risks and potentially leading to land loss.

This study examines factors driving peat decomposition, with emphasis on deeper, water-saturated zones and the dynamic transition zone where groundwater levels fluctuate. Laboratory and field experiments investigated the effects of oxygen availability, plants that makes the peat, historical drainage, compaction, and redox conditions on microbial activity.

Key findings show that plant type, iron, and sulphur are determining factors for the decomposition rates, especially in transition zones. Mechanical compaction temporarily reduces porosity and thus decomposition. Rewetting reduces COâ‚‚ emissions but can increase CHâ‚„ emissions, depending on location and peat type. Measurements of redox profiles and microbial activities improve the estimation of greenhouse gas emissions. This research contributes to a better understanding of peat decomposition and provides first steps for effective management and restoration of drained peat systems.