Can we accurately model peatland complexity? Analysing simulations of the Holocene Peat Model and observations from four peatlands in the James Bay lowlands, Eastern Canada.

Anne Quillet¹*, Michelle Garneau², Steve Frolking³ and Nigel Roulet^4
1 Institut des Sciences de l’Environnement & Géotop, Université du Québec à Montréal (UQAM), Montréal, Qc., Canada (quillet.anne@courrier.uqam.ca)

² Département de Géographie & Géotop, UQAM, Montréal, Qc., Canada

³ Institute for the Study of Earth, Oceans, and Space & Dept. of Earth Sciences, University New Hampshire, Durham, NH, USA

⁴ Departement of Geography & McGill School of Environment, McGill University, Montréal, Qc., Canada.

The Holocene Peat Model (HPM, Frolking et al. in preparation) is a simple dynamic model simulating the transient evolution of a peatland since its early stages. This new model combines two earlier models: the Peat Accumulation Model (Hilbert et al. 2000) and the Peat Decomposition Model (Frolking et al., 2001). HPM has an integrated dynamics and takes into account the feedbacks between vegetation, peat properties, water table depth, and climate.
The aim of this study is to evaluate the ability of the HPM to reproduce the peatland dynamics like it is observed in subarctic and boreal peatland in Québec. We argue that if the model is able to reproduce the dynamic for different sites, it would be able to simulate peatland dynamics for other regions.
The second objective of this study is to investigate the role of the environmental conditions on the peatland dynamics as well as on the carbon balance in peatlands.
Multiple paleaoecological datasets are used to assess the representativeness of the model. Four distinct sampling sites are chosen within a large region including boreal and subarctic ecosystems in the Bay James lowlands, northern Québec, Canada. One fen and one bog are selected in the subarctic region and two bogs in the boreal region. These sites have different geographical, climatological and ecological features (ex. pH, nutrient availability and species compositions). A central core from each site is dated with ²¹⁰Pb and ¹⁴C, analysed against loss on ignition and plant macrofossils.
Moreover, testate amoebe analyses (3 of the 4 sites) allow us to reconstitute the water table depth in our selected peatlands during their development with help of a transfer function (Booth, 2007).
A sensitivity analysis on the parameters of the model has been achieved and the model has been constrained in several ways to capture the causes of the biases between the simulations and the observations.
It can be conclude that both the hydrological routine and the accumulation-decomposition balance play a strong role in the simulations. Furthermore, we expect the study to push forward the role of the water table depth in the carbon and peat accumulation dynamics.

Schematic description of the Holocene Peat Model (HPM)
Booth, R.K. 2007. Testate amoebae as proxies for mean annual water-table depth in Sphagnum-dominated peatlands of North America. Journal of Quaternary Science, vol. 23, no 1, 43-57.
Frolking, S., Roulet, N.T., Moore, T. et al. 2001. Modeling Northern Peatland Decomposition and Peat Accumulation. Ecosystems, vol.4, 479-498.
Frolking, S., Roulet, N.T., Tuittila, E., Bubier, J.L., Quillet, A. A new model of long-term peat accumulation, in preparation.
Hilbert, D.W , Roulet, N.T., and Moore, T. 2000. Modelling and Analysis of Peatlands as Dynamical Systems. Journal of Ecology, vol.88, 230-242.

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