Mika Yli-Petäys and Harri Vasander
After Wise Use – The Future of Peatlands, Proceedings of the 13th International Peat Congress: Peatland After-Use
Cutaway peatlands are net sources of carbon (C) to the atmosphere as the residual peat gradually decomposes. The release of C to the atmosphere can be stopped by rewetting. Further, the re-establishment of Sphagnum and sedge species may lead to the recovery of the C sink. The role of sedges in the C balance is slightly two- sided. As well as being large sinks of CO2, sedges also promote high CH4 emissions via their aerenchymatic tissues. As high water levels promote high CH4 emissions, lowering of the water levels has sometimes been suggested as an option for minimising the CH4 emissions from restored peatlands. On the other hand, the photosynthetic activity of the plants will decrease in low water levels. We measured the gas exchange of three sedge species (Eriophorum vaginatum, E. angustifolium and Carex rostrata) and a moss Sphagnum fallax in an experimental site where the water levels were regulated. Our results showed that C sinks in restored peatlands may be optimised by adjusting the water levels. High water levels close to the peat surface were found to be optimal for all the studied plant species and, in terms of GWP, the sedge plots even contributed to a net cooling effect.