CARBON DYNAMICS IN BOREAL PEATLANDS, LA GRANDE RIVER AREA, JAMES BAY LOWLANDS, QUÉBEC, CANADA

The James Bay region presents interesting challenges to the determination of the “natural” GHG sink/source properties of the wetlands. The preliminary study of Garneau et al. (2001) was the first study related to climate change and carbon dynamics in the region, even though it is part of the largest peatland complex in North America. The overall objective of this integrated study is the comprehension of mechanisms that will influence peatland dynamics and vulnerabilities under predicted changing climate along Quebec James Bay lowlands where peatlands cover more than 50% of the territory (Tarnocai et al., 2000). The multidisciplinary research project integrates multiple-sources of data from complementing fields such as remote sensing, ecology and biogeochemistry, particularly greenhouse gas exchange, and paleostratigraphic analyses (geomorphology and paleoecology). Analysis of remote sensing is used to provide the mapping of present-day and reconstruction of past surface peatlands characteristics and extent. Peatlands surface conditions are hindcasted from meteorological time series to reconstruct past hydrological conditions through the last decennia. Remote sensing analyses is also used to estimate and characterize surface peatlands cover. Peatlands are sampled for CO₂ and CH₄ measurements and modelling using the PCARS model (Frolking et al., 2001, 2002) to assess the variability of carbon and CH₄ exchange over the period of record and to determine the relative sensitivity of the exchanges in future climate scenarios. The link between contemporary and past exchanges is developed by carrying out paleo-reconstructions (pollen and macrofossils) based on the same peatlands used for contemporary measurements of the GHG exchanges. To identify past favourable conditions for carbon accumulation, a sequential reconstruction of the peatlands and their related carbon accumulation is realized through Holocene (using relative and absolute chronology) to allow comprehensive spatial and temporal understanding of their dynamics from the time they first began accumulating carbon to their present day patterns and processes in boreal Quebec. This research is supported by a NSERC-CRD collaborative research project with Hydro-Quebec.