Modelling and analysis of peatlands as dynamical systems

1 A general model of peatland dynamics is presented that emphasizes the interaction between water table depth and peat production. The model consists of two coupled, non-linear differential equations representing change in depth of peat and depth to the water table. Several simplified models are also considered to show the logical development of this model from previously published ones. The model provides an integrated view of how peatlands function over long time scales, by focusing on the non-linear interactions among peat production, decomposition and hydrology. 2 Analysis of the model shows that equilibrium peat accumulation and water table depth depend on the net water input to the peatland. In drier sites, peatlands with relatively deep water tables develop and the equilibrium peat depth increases with increasing water input. In very wet conditions, peatlands have water tables near the surface, peat accumulation is limited by low production rates, and equilibrium peat depth is lower than is possible in comparatively drier sites. Over a range of intermediate water balances, there are two simultaneous equilibrium states where deep, dry peatlands and shallower, wet peatlands can both occur. This sensitivity to water balance suggests that small changes in precipitation regime, such as are expected with climate variability and change, could rapidly convert peatlands that are now in equilibrium into either sources or sinks of carbon.