Short-term effects of changing water table on N2O fluxes from peat monoliths from natural and drained boreal peatlands

The effect of the water table on nitrous oxide (N2O) fluxes from pear profi les representing boreal peatlands of differing nutrient status was studied in the laboratory. Lowering of the water table in peat monoliths taken from two natural waterlogged peatlands for 14 weeks in a greenhouse at 20 degre es C increased the fluxes of N2O, an effect that was enhanced further by in cubation in the dark. Raising of the water table in monoliths from two drai ned and forested peatlands caused cessation of the N2O fluxes from the drai ned peats, which had previously been sources of N2O. It is known that N2O f luxes have increased in peatlands drained several decades ago. The results suggest that it is not necessary for the water table to be lowered for seve ral years to change a boreal peatland from a N2O sink to a source of the ga s. In addition to the draining of peatlands, climate change can be expected to lower ground water levels during the summertime in the boreal zone, and this could cause marked changes in N2O fluxes from boreal peatlands by enh ancing the microbial processes involved in nitrogen transformations.