CELL-BASED SIMULATION OF PEAT ACCUMULATION IN NORTHERN PEATLANDS

Northern peatlands, such as the Glacial Lake Agassiz Peatlands, contain nearly one third of the carbon stored in global soils. Depending on the response of these peatlands to temperature and hydrologic change, they could function as either important carbon sources or carbon sinks. To evaluate peatland response to changes in climate we have prepared a computer model that simulates peat accumulation using stochastic cellular automata within a rectangular lattice. In contrast, other research groups have simulated peat accumulation based on an analytical solution of differential equations. Starting with a basin of geologic sediment, 10 cm thick peat blocks are randomly added at the sediment-atmosphere interface based on a probability consistent with the average peat production rate of 10 cm per 44 years. Decay is managed in a similar manner with cells randomly transforming through different degrees of humification and becoming more recalcitrant and less likely to decay with increasing humification. To simulate decreasing mass with decay, when cells in the model undergo initial decay, the cell combines with the cell above it so that the characteristics of the two cells (age of deposition, decay state) are combined into one cell. When cells reach the final decay state they collapse without combining their traits with the cell above. This simulates the peat cell reaching negligible mass. Preliminary runs of the peat accumulation models produce peatlands with net production rates averaging 1.3x10^-1 cm year^-1, which is on the upper end of the previously reported range of peat accumulation values. This research will be linked to a hydrologic model to evaluate feedbacks between peat growth, decay, and groundwater flow processes.