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Peatlands constitute major sinks of organic carbon (C) and play a key role in the global C cycle. Here, we present a synthesis of peat records from six ecoclimatic regions in Québec, Canada, in order to quantify Holocene patterns of C accumulation and relationships with contemporary climate data. Average long-term apparent rates of C accumulation (LORCA) were calculated for 21 peat cores and range from 10 to 70 g C/m2/yr with a mean of 26.1 (standard error of mean (SEM) = 3.6) g C/m2/yr, which is slightly higher than the mean value for northern peatlands as a whole (Loisel et al., 2014). We found that regional climate has been a major factor controlling long-term peatland C accumulation and that site-specific factors may explain some variability between sites. Our data show that LORCA tend to decrease with latitude. The lowest LORCA are found in the northernmost peatlands located at the boreal forest/forest-tundra ecotone, whereas the highest values are recorded in the peatlands along the St. Lawrence Estuary, characterized by the highest mean summer temperature, number of growing degree-days above 0°C and mean annual precipitation. Temporal variations in Holocene C accumulations rates were synthesized for 16 peat cores, which show high values during the mid-Holocene (6000–4000 cal. yr BP) followed by a decline during the Neoglacial cooling, especially between 2000 and 1200 cal. yr BP. Our study contributes to a better understanding of sensitivity of peatland C balance to climate change in a poorly documented part of the circumboreal region.

Northern peatlands act as archives of environmental change through their sensitivity to water balance fluctuations, while being significant contributors to global greenhouse gas dynamics. Subarctic fens in north-eastern Canada are characterized by a dominance of pools and flarks. We aimed to reconstruct the late Holocene hydrological conditions of these fens to establish the timing of the initiation of pool and flark formation and possible links with climate. Testate amoebae and plant macrofossils from five cores, sampled in three fens, were analysed to infer water tables with chronologies based on 14 C and 210 Pb dating. All sites showed the presence of relatively dry, ombrotrophic conditions with abundant Picea from 5000 cal a BP, followed by a first shift to wet, poor fen conditions with pool and flark development around 3000 cal a BP and a subsequent wet shift after $800 cal a BP. These trends coincide with previously observed Neoglacial and Little Ice Age cooler and wetter conditions and therefore climate may well have been a dominant factor in the initiation and development of pools and flarks over the late Holocene. The effect of anticipated climate change on subarctic peatlands remains unclear, although wetter conditions might enhance pool expansion to the detriment of terrestrial components.