Boreal peatland CO₂ - CH₄ fluxes linked with a precipitation increase climate scenario, Quebec, Canada.

Luc Pelletier and Michelle Garneau
Departement of Geography and Geochemistry and Geodynamics Research Center Université du Québec à Montréal (pelletier.luc@uqam.ca)

Peatlands play an important role in the C cycle and climate, storing approximately 1/3 of the soil C and being the largest natural terrestrial source of atmospheric methane (Frolking et al. 2006). The most recent climate scenarios predict increases in mean annual temperature and important changes in precipitation regimes and intensity. These global changes will have significant impacts on C dynamics of boreal peatlands. Several studies on CO2 and CH4 dynamics have shown that strong summer drought or water table drawdown can lead to a loss of C (e.g. Strack et al. 2007). In boreal Quebec, Canada, climate scenarios predict an increase in temperature and precipitation (Lemmen et al., 2007). Here we present results from a 3 years study on CO2 and CH4 fluxes in a boreal peatland looking at flux variations in relation with environmental controls (e.g. temperature, water table depth). Fluxes were measured during 3 growing seasons using static chambers and following a microtopographic gradient from high hummock, low hummock, lawn and wet depression. Overall, results for CH4 fluxes show small year-to-year variations for all sites. On the other hand, significantly larger CO2 uptakes were measured during growing season with highest water table (2008) on the high and low hummocks microforms (Figure 1). The rise in water table depth in 2008 also inhibited CO2 absorption on the wet depression microforms but had almost no effect on the lawns. These results combined to climate scenarios suggest that Quebec’s boreal peatland surface fluxes and microforms dynamics could be greatly modified in the future. These changes could accentuate the differences in fluxes between the microforms and the overall peatland C budget.

Frolking, S., Roulet, N.T. and Fuglestvedt, J. 2006. How northern peatlands influence the Earth’s radiative budget: Sustained methane emission versus sustained carbon sequestration. Journal of Geophysical Research 111: G01008, doi: 10.1029/2005JG000091.
Lemmen, D.S., Warren, F.J., Lacroix, J., and Bush, E., editors, 2008. From Impacts to Adaptation: Canada in a Changing Climate 2007; Government of Canada, Ottawa, ON, 448 p.
Strack, M. and Waddington J.M. 2007. Response of peatland carbon dioxide and methane fluxes to a water table drawdown experiment. Global Biogeochemical Cycles. 21, GB1007, doi: 10.1029/2006GB002715.

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