The understanding of past and present-day carbon dynamics of boreal peatlands, James Bay Lowlands, Quebec, Canada

In boreal regions of the northern hemisphere, peatlands cover up to 20% of the Canadian territory, and between 9 to 12% of the Quebec province. Considering that peat accumulation is thought to be largely a function of moisture and temperature, we developed a multidisciplinary approach in order to improve the understanding of peatland carbon dynamics in the James Bay Lowlands region (51-54°N; 73-78°W). Ten peatlands representative of the ecogeomorphic areas from which they belong were investigated and provide data from paleoecology, biogeochemistry, surface fluxes and related vegetation. Local and regional variability of surface CO2 and CH4 exchanges were determined to detail the relative sensitivity of the peatland carbon fluxes in relation with current climate conditions (WTD) and nutrient context (bogs vs fens). Isotopic fractionation (δ C13) of surface and subsurface vegetation as well as peat and carbon accumulation reconstructed from the beginning of peat inception in the region ( ca 7000 BP) until the last centuries ( ca 250 yrs) were achieved using radiochronology (210Pb and 14C), carbon content (LOI and C/N), microfossils (pollen, spores and testate amoebae) and plant macrofossils. Detailed analyses of the peatlands show that even the general peat accumulation models present relatively accurate estimates of LORCA and peat depths, the balance between C input and decay has changed considerably (LORCA range 11-59 g m-2 yr-1) during the development of the peatlands. These data provide spatial and temporal understanding of northeastern canadian boreal peatlands from the time they first began accumulating carbon to their present day patterns and processes. This research is supported by NSERC (Natural Sciences and Engineering Research Council of Canada) and Hydro- Québec.