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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
1Department of Geography, McGill University, 805 Sherbrooke Street West, Montreal, QC H3A 2K6, Canada
2The Global Environment and Climate Change Centre, McGill Univ., 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
5Dept. of Geography, Trent Univ., 1600 Westbank Drive, Peterborough, ON K9J 7B8, Canada
6Dept. of Geography and 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, PO Box 1700, STN CSC, Victoria BC V8W 2Y2, Canada
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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 [g C
m−2 d−1]: 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 modest
temperature increases could lead to converting the bog from a sink to a
source of CO2. General weaknesses and further developments of MWM are
discussed.
Discussion Paper (PDF, 1263 KB) Interactive Discussion (Final Response, 3 Comments)
Citation: St-Hilaire, F., Wu, J., Roulet, N. T., Frolking, S., Lafleur, P. M., Humphreys, E. R., and Arora, V.: McGill Wetland Model: evaluation of a peatland carbon simulator developed for global assessments, Biogeosciences Discuss., 5, 1689-1725, 2008. Bibtex EndNote Reference Manager
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