A Markov chain method for simulating bulk density profiles in boreal peatlands

Abstract Bulk density is a key determinant of numerous physical characteristics in peat including hydraulic conductivity, smouldering combustion vulnerability, and water retention in the unsaturated zone. A Markov chain model based on peat type (primarily Sphagnum, sedge, and sylvic peats) was applied to the depth-wise structure of boreal peatlands using 143 cores from western Canada as source data. Bulk density and peat type were modelled in 2160 simulated peat profiles by driving Markov chains associated with bulk density distributions by peat type and depth. The model closely reproduced the expected change in bulk density between vertically adjacent peat horizons. Markov-derived peat profiles showed somewhat greater variance in organic matter load in the upper 135 cm compared to observed cores due to the lack of whole-profile bias or trends in density. The method and derived Markov chains shown here have utility in hydrological modelling, regional carbon estimates, and in the modelling of disturbances such as wildfire.