Decomposition of Scots pine litter and the fate of released carbon in pristine and drained pine mires

A field experiment was carried out to validate the results of a previous laboratory experiment showing that part of the carbon released from decaying Scots pine (Pinus sylvestris L.) needle and fine root litter was retained in the peat soil. 14C-labelled litter was incubated for up to 1.5 years in pristine and drained peat soils. During this period, 40–60% of the initial 14C-activity was lost from the litter and 10–30% of the lost activity was retained in the soil. Needle litter decomposed faster than fine root litter. On average, drainage increased the mass and 14C losses from the needle litter in Carex-peat but not in Sphagnum-peat. Losses from the fine root litter were not clearly affected by drainage. Drainage did not significantly affect the relative proportion of 14C-activity found in the peat. The results support the earlier hypothesis that a flow of organic C from decaying tree litter contributes to C storage in drained peatlands.