Stable carbon isotopic composition of peat columns, subsoil and vegetation on natural and forestry-drained boreal peatlands.

We studied natural and forestry-drained peatlands to examine the effect of over 34 years lowered water table on the δ13 C values of vegetation, bulk peat and subsoil. In the seven studied sites, δ13 C in the basal peat layer was 1.1 and 1.2 ‰ lower than that of the middle-layer and surface layer, respectively. Furthermore, there was a positive correlation between the δ13 C values of the basal and surface peat layers, possibly due to carbon (C) recycling within the peat column. In the same mire complex, natural fen peat δ13 C values were lower than those of the nearby bog, possibly due to the dominance of vascular plants on fen and the generally larger share of recycled C in the fens than in the bogs. Furthermore, natural and 51 years previously drained fen and bog, on the opposite sides of a ditch on the same mire complex, showed no significant differences in δ13 C values. Plant δ13 C values were lower, while δ13 C values of subsoil were higher in the drained than in the natural site of the fen.