Climatic and autogenic control on Holocene carbon sequestration in ombrotrophic peatlands of maritime Quebec, eastern Canada

Ombrotrophic peatlands (bogs) act as important terrestrial sinks of organic carbon (C). These ecosystems are widespread in coastal maritime regions of eastern Canada. This study aims to evaluate and compare Holocene peatland C dynamics between two maritime ecoclimatic regions along the St. Lawrence North Shore. The investigated bogs are located on two postglacial deltas along the Estuary (Baie-Comeau) and the Gulf of St Lawrence (Havre-St-Pierre) in eastern Quebec. Long-term apparent rates of C accumulation (LORCA) are calculated for eight peat cores, and temporal variations in C accumulation are compared between six peatlands. Our data suggest that long-term C sequestration is affected by a constant anoxic decay, but the LORCA are considerably lower in Havre-St-Pierre (16-46 g C/m(2)/yr) than in Baie-Comeau (53-68 g C/m(2)/yr). The interactions between water table levels, peat humification and C accumulation are also evaluated and suggest an influence of internal (autogenic) processes and feedbacks. The bogs of the two regions show distinct patterns of C sequestration and different sensitivities to climate especially during the late Holocene. These results show that in spite of the internal influences, the regional climate has exerted a pervasive control on primary production in these peatlands over the Holocene.