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?