Assessment of an integrated peat-harvesting and reclamation method: peatland-atmosphere carbon fluxes and vegetation recovery

We document a two-year experimental trial of a recently-developed integrated peat-harvesting and reclamation technique at a poor fen in northern Ontario, Canada. We removed and conserved the uppermost ~0.3 m of peat in blocks while deeper peat was harvested from the resultant pit. We allowed the extraction pit to flood with shallow groundwater, and then reclaimed the conserved surficial peat blocks by transplanting them into the flooded pit where they formed a low, floating mat. In the 2nd year after harvest average Sphagnum cover in our experimental plot was intermediate (~25 %) between hummocks (~100 %) and hollows (~10 %) at an adjacent unharvested reference plot. Mean rates of Sphagnum productivity were greater in the experimental plot (65–86 g m−2 month−1) than in the reference plot (45–55 g m−2 month−1) for both hummock (S. fuscum) and lawn (S. magellanicum) species, although not significantly so, indicating that the transplant had no adverse effects on Sphagnum health. The inundated soil conditions in the trial pit prevented the large carbon dioxide emissions that are characteristic of many harvested peatlands. During the second growing season midday net ecosystem exchange at the experimental plot was similar to that at hollows in the reference plot. However, the anoxic soil conditions in the experimental plot led to highly elevated methane emissions in both years. Our results demonstrate that the method can enable rapid re-establishment of a healthy Sphagnum mat and carbon dioxide sequestration function in harvested peatlands, although the global warming potential of our experimental trial was high due to elevated methane emissions.