Wildfire Impacts on Peatland Ecohydrology

Abstract

<p>The objective of this thesis is to examine the changes to peatland ecohydrological processes as a result of wildfire disturbance in forested ombrotrophic peatlands of the Boreal Plains. The hydrology and atmospheric exchanges of energy and water were examined at two peatlands in northern Alberta: one recently burned and the other approximately 75 years since fire.</p> <p>Wildfire resulted in little change in net radiation flux to the peatland during the snow-free period. A decrease in the net radiation flux during the late winter was caused by the loss of the tree canopy and the increase in albedo during winter. While summer albedo largely returned to pre-fire values within two years after fire, the amount of solar radiation reaching the burned peat surface increased by nearly 50%. As a result, surface evaporation increased by an amount only marginally greater than the loss of transpiration. The net result on the water balance was a modest increase in water losses during the course of the summer, resulting in a lower water table. Water table decline per unit of evaporation was higher due to a decrease in specific yield, likely from a combination of post-fire peat compression and the combustion of high specific yield surface peat during wildfire. The combination of lower water table and enhanced evaporation cause greater pore-water pressures after fire, particularly in hummocks. The hydrological regime of hollows was not significantly altered by wildfire, despite the larger depth of burn in the hollows.</p>