Legacy of peatland erosion shapes microbial communities during recovery

Human degradation of peatlands worldwide has turned them into net carbon sources. In upland blanket peatlands, erosion disrupts new plant-derived carbon input and exposes deep peat, putting old carbon at risk of oxidation. The efficacy of restoration in preventing carbon loss and recovering ecosystem function depends on microbial responses to both water table manipulation and renewed litter input. Yet it is unclear how these factors alter the microbial communities that ultimately control carbon storage and emissions. We show that microbial community composition in the eroded peatland of Waun Fignen Felen, South Wales, was primarily governed by the bioavailability of organic matter rather than water-table position. Long-term erosion leaves behind a legacy of highly degraded organic matter, unaltered by re-wetting. Where plant litter accumulation is renewed on formerly eroded peat surfaces, the influx of bioavailable organic input supports a distinct microbial community with greater biomass, and evidence of elevated respiration.