A Model of Organic Matter Accumulation in a Developing Fen/Raised Bog Complex

A mechanistic simulation model of organic matter accumulation for a developing fen/raised bog complex in Ireland is presented. Parameter/variable values have been primarily drawn from the published literature. The development of the theoretical considerations of fen peat as a substratum to a raised bog is evaluated using the model. Terrestrialization is the pathway of hydroseral succession. The conceptual model treats peat growth as the accumulation of a series of parcels comprising both a labile and a non-labile component. The fen phase of the model uses a discrete description of organic matter accumulation while the raised bog phase uses a continuous description. Both phases use a constant decay rate. The model integrates changes in net primary productivity and aerobic decay to simulate four climatic periods. It generates outputs for peat depth and mass with time and profiles of bulk density with depth. Results over a simulated period of 10 000 years demonstrate how changes in surface net primary productivity and aerobic decay can change the rate of peat accumulation in the developing fen/raised bog complex. Sensitivity analysis showed that the most important parameters influencing simulated depth and mass were the labile fraction in organic matter of the raised bog followed by its net primary productivity. The potential significance of underlying fen peat as a proportion of the total depth and mass of a developing fen/raised bog complex was evaluated and shown to be substantially diminished after 5000 years. It was established that the model predictions corresponded well with data for Irish Midland bogs and that given suitable adjustment of values, could potentially simulate Fennoscandian conditions as well.