Net ecosystem CO2 exchange of a cutover peatland rehabilitated with a transplanted acrotelm

Natural peatlands are an important component of the global carbon cycle, representing a net long-term sink of atmospheric carbon dioxide (CO2). The natural carbon storage function of these ecosystems can be severely impacted due to peatland drainage and peat extraction, leading to large and persistent sources of atmospheric CO2 following peat extraction abandonment. Standard restoration techniques aim to restore the peatland to a carbon-accumulating system through various water management techniques to improve hydrological conditions and through reintroducing Sphagnum at the surface. However, restoring the hydrology of peatlands can be expensive due to the cost of implementing the various restoration techniques. This study examines the net ecosystem CO2 exchange of a new extraction—restoration technique where the acrotelm is preserved and replaced directly on the cutover surface. Peat respiration at the experimental restored acrotelm (110.5 g C·m−2over the study period: May 20–August 18) was significantly lower than at the natural peatland (144.8 and 203.7 g C·m−2, wet and dry plots respectively). However, gross ecosystem production (GEP) at the experimental site was significantly reduced (-54.0 and -34.4 g C·m−2) compared to the natural site (-179.2 and -162.0 g C·m−2). Consequently, this was a growing season net emitter of CO2 to the atmosphere over the season at the experimental site (78.5 and 56.5 g C·m−2 and a growing season sink of CO2 at the natural site (-17.6 and -22.8 g C·m−2). Light response curves indicated that maximum GEP was significantly lower at the experimental site; however, it is likely that the percentage of living and dead vegetation at the plots post restoration had a large control on this lower productivity as plots with more living vegetation had higher overall productivity (GEP). Nevertheless, the experimental site did maintain limited productivity post-extraction, indicating that the carbon dynamics of the system was maintained due to this acrotelm restoration process, thereby likely returning the ecosystem toward a natural sink of atmospheric CO2 faster than natural rehabilitation and current restoration techniques. As such, this approach to peat extraction may be an environmentally preferred approach to use.