High-resolution carbon pool estimation at peatland scale using ground-penetrating radar and paleoecological data

Pierre-Luc Dallaire¹, Michelle Garneau¹ and Bernard Giroux^2
1 Département de Géographie and Centre de recherche Géotop, Université du Québec à Montréal, Montréal, Québec, Canada. (plucdal@hotmail.com)
² Département des génies civil, géologique et des mines, École Polytechnique de Montréal, Montréal, Québec, Canada.

Boreal peatlands store large amount of carbon (C) through peat accumulation. Global climate change could induce important return of C to the atmosphere (Takeshi et al. 2008). Thus a more accurate estimation of C distribution is required to evaluate such predicted impacts (Limpens et al. 2008). Most studies evaluating sequestered C have been made at regional or global scale. Here, we calculated the stored C in a 2,4 km² ombrotrophic peatland located in northern Québec using a ground-penetrating radar (GPR) in order to estimate if peatland scale studies can improve previous estimation of global sequestrated carbon. The GPR is a geophysic technique based on the electrical properties of the ground and largely controlled by its water content (Davis and Annan, 1989). It allows a continuous imagery of the dominant stratigraphic layers in sediments. More than 6,4 km of GPR transects were collected during summer 2008. Peat thickness was also measured manually using a Hiller corer and surface altitude obtained with a differential global positioning system (DGPS). For stratigraphic corroboration , five cores were collected using a Russian peat sampler. The interpretation of the GPR results has been validated with field data (e.g. a 10m trench, water conductivity, peat layers permittivity andwater-table measurements) and paleostratigraphic analyses (e.g. loss-on-ignition, Troels-Smith description). Two main stratigraphic layers were correlated with the GPR profiles: the fen-bog transition at the base of the cores and a stratigraphic change is also detectable at the near surface. Those layers have distict peat properties (e.g. bulk density) affecting the carbon budget estimation. More, the GPR results allow a more accurate peat thickness compared the the cored measurements. Incorporated into a geographic information system (GIS), we used the dataset to develop a 3D model where the interpolation of the differents layers was performed to represent the whole peatland. and estimate with precision, its total carbon pool.

Limpens, J., F. Berendse, C. Blodau, J.G. Canadell, C. Freeman, J. Holden, N. Roulet, H. Rydin et G. Schaepman-Strub. 2008. «Peatlands and the carbon cycle: from local processes to global implications - a synthesis». Biogeosciences. vol. 5, p. 1475-1491.
Davis, J. L., et A.P. Annan. 1989. «Ground-penetrating radar for high-resolution mapping of soil and rock stratigraphy». Geophysical Prospecting. vol. 37, p. 531-551.
Takeshi, Ise, Allison L. Dunn, Steven C. Wofsy et Paul. Moorcroft. 2008. «High sensitivity of peat decomposition to climate change through water-table feedback». Nature geoscience. vol. 1, p. 763-766.

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