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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 7, issue 11
Biogeosciences, 7, 3517–3530, 2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Peatlands and the carbon cycle – from local processes to global...

Biogeosciences, 7, 3517–3530, 2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  09 Nov 2010

09 Nov 2010

McGill wetland model: evaluation of a peatland carbon simulator developed for global assessments

F. St-Hilaire1,2, J. Wu1,2, N. T. Roulet1,2,3, S. Frolking4, P. M. Lafleur5, E. R. Humphreys6, and V. Arora7 F. St-Hilaire et al.
  • 1Department of Geography, McGill University, 805 Sherbrooke Street West, Montreal, QC H3A 2K6, Canada
  • 2The Global Environment and Climate Change Centre, McGill University, Montreal, QC, Canada
  • 3McGill School of Environment, McGill University, Montreal, QC, Canada
  • 4Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA
  • 5Department of Geography, Trent University, 1600 Westbank Drive, Peterborough, ON K9J 7B8, Canada
  • 6Department of Geography & Environmental Studies, Carleton University, B349 Loeb Building, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
  • 7Canadian Centre for Climate Modelling and Analysis (CCCma), Environment Canada, P.O. Box 1700, STN CSC, Victoria, BC V8W 2Y2, Canada

Abstract. We developed the McGill Wetland Model (MWM) based on the general structure of the Peatland Carbon Simulator (PCARS) and the Canadian Terrestrial Ecosystem Model. Three major changes were made to PCARS: (1) the light use efficiency model of photosynthesis was replaced with a biogeochemical description of photosynthesis; (2) the description of autotrophic respiration was changed to be consistent with the formulation of photosynthesis; and (3) the cohort, multilayer soil respiration model was changed to a simple one box peat decomposition model divided into an oxic and anoxic zones by an effective water table, and a one-year residence time litter pool. MWM was then evaluated by comparing its output to the estimates of net ecosystem production (NEP), gross primary production (GPP) and ecosystem respiration (ER) from 8 years of continuous measurements at the Mer Bleue peatland, a raised ombrotrophic bog located in southern Ontario, Canada (index of agreement [dimensionless]: NEP = 0.80, GPP = 0.97, ER = 0.97; systematic RMSE [g C m−2 d−1]: NEP = 0.12, GPP = 0.07, ER = 0.14; unsystematic RMSE: NEP = 0.15, GPP = 0.27, ER = 0.23). Simulated moss NPP approximates what would be expected for a bog peatland, but shrub NPP appears to be underestimated. Sensitivity analysis revealed that the model output did not change greatly due to variations in water table because of offsetting responses in production and respiration, but that even a modest temperature increase could lead to converting the bog from a sink to a source of CO2. General weaknesses and further developments of MWM are discussed.

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