The effect of disturbance on the biogeochemical cycling of carbon in northern forest soils

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Forest harvesting and wildfire disturb the carbon cycle in the soils of the boreal forest in fundamentally different ways. During harvesting mechanical disturbance physically mixes organic matter from the organic layer into the mineral soil while combustion of the organic layer in a fire chemically transforms organic matter and produces ash and char that increases the pH and releases nutrients. Despite the widespread occurrence of fire and harvesting, there are few investigations comparing the effects of fire and harvesting on the carbon cycle in the soil, and fewer still that consider the entire soil profile. Findings from the few available studies indicate that SOC stored below 30 cm in harvested forests increases significantly in the years immediately following disturbance and declines through time. Is this carbon transported from the surface, in what form and at what rate? Is it mineralized in situ or does it get exported from the system? In fire affected forests, transport of surface organic matter appears to be limited to the A horizon, which is surficial and typically thin. Why? ***Over the next five years my research program will focus on examining and comparing the transformation and transport of SOC in wildfire and harvested mixed wood boreal forests with the specific objectives of: 1. quantifying rates of transport of SOC in the profile, 2. identifying mechanisms of SOC stabilization and destabilization through the profile, and 3. assessing the bioavailability of buried and burned SOC stores***Meeting the short term objectives of my program will continue to my career goals of: 1. improving our understanding of the effects of environmental perturbation on the biogeochemical cycling of SOC in terrestrial systems and 2) advancing the use C isotopes and novel molecular techniques, in conjunction with more classical biogeochemical approaches (e.g. physical fractionation). ***Directly complementing work underway by my provincial and national governmental colleagues, this research will assist in guiding carbon and forest management policy issues around climate change and biomass for bioenergy. My research program will train students in cutting edge and classical methods in biogeochemistry and develop skills in asking and answering critical questions in the biogeochemical cycling of C. The interaction between students, government scientists and academics will enhance student understanding of and experience with the relevance and applications of research in policy and management.