Epsilon Open Archive

Abstract

Peat extraction for horticultural purposes and energy production has a long tradition in Northern Europe. Related drainage activities directly affect the greenhouse gas (GHG) balance due to oxidative peat decomposition and denitrification, with concomitant emissions of carbon dioxide (CO₂) and nitrous oxide (N₂O). Rewetting, i.e. raising of the water table, is one after-use and restoration objective. Rewetting transforms an extracted peatland with aerobic soil conditions into a wetland with prevailing anaerobic conditions and can thus create suitable conditions for peat-forming plants, which could restore carbon (C) storage functions. Studies on GHG emissions from extracted peatlands after rewetting are limited. In general, peatland rewetting decreases emissions of CO₂ and N₂O, while methane (CH₄) emissions may increase. More data are needed on GHG emissions from extracted peatlands over longer periods after rewetting and from corresponding studies about constructed water bodies and their vegetated littoral zones, which have been identified as high CH₄ emitters.

Studies were investigated how typical peatland ecotopes and vegetation communities created after rewetting affected CO₂, CH₄ and N₂O emissions. Specific objectives were to determine the relationships between GHG emission fluxes and water conditions, soil/water temperature and vegetation cover. GHG emission fluxes were measured in two rewetted extracted peatlands in Sweden using manual opaque and automated transparent chambers for discontinuous and continuous measurements, respectively.

The overall climate impact of CH₄ emissions from the study areas did in general not exceed the impact of soil and plant respiration and neither the net CO₂ flux during summer. But, GHG emissions could vary between years and sites can shift from sinks to sources. In regards to management of extracted peatlands, the construction of shallow lakes showed great potential for lowering GHG fluxes to the atmosphere.

With continuous measurements a derivation of long-term gas balances can be achieved and short-term changes in environmental conditions influencing GHG exchanges can be detected more effectively as with discontinuous measurements, such as by vial sampling. But still, a correct indication of all GHG fluxes, e.g. for GHG upscaling purposes or national emission inventories, is strongly based on the correct estimation of all C fluxes including ebullition.