The Holocene Peat Model (HPM, Frolking et al. 2010) integrates up-to-date knowledge on peatland dynamics and explores peatlands development and carbon dynamics on a millennial timescale. HPM combines the water and carbon cycles with net primary production and peat decomposition from 12 plant functional types and takes the multiple feedbacks into account. The model remains simple and few site-specific inputs are needed. HPM simulates the transient development of the peatland and delivers peat age, peat depth, peat composition, carbon accumulation and water table depth for each simulated year.

The work presented here aims at analysing the role of each component of the system on peatland dynamics. First, the influence of the model parameterization on the simulation results is examined. Therefore, a sensitivity analysis is performed with use of a screening method (Morris’ elementary effects and extended elementary effects methods, Morris, 1991, Campolongo et al. 2007) and with calculation of the Sobol’ indices (Sobol’, 1993). These methods rank parameters and combinations of them according to their influence on simulation results and allow the identification of non influential parameters. Second, paleo-ecological data (testate amoebae and plant macrofossils) from James-Bay lowlands in Québec (Canada) are used to force the model and test its response against real site-data.

Results emphasize the role of environmental conditions (e.g. precipitation, runoff, and potential productivity) and thus highlight the need for further research in the representation of runoff in peatlands over large areas. The role of Sphagnum is also stressed since Sphagnum species may lead to major changes at different stages in the development of the system.