• Friedland, Andrew J.
  Dartmouth Environmental Studies Program
  andy.friedland@dartmouth.edu
  

Changes in soil respiration associated with effects of forest harvesting could increase net loss of CO2 to the atmosphere relative to pre- harvest values. By excavating quantitative soil pits across a gradient of physical disturbance in a harvested northern hardwood forest, this study examined C release from mineral soil. Mineral soil samples were analyzed for pH, percent organic matter (%OM), C and N concentration, δ13C, and total C per unit area. Results show a relationship between degree of disturbance and C concentration in soil 10-30 cm beneath the O-horizon. Highly disturbed sites show C depletion, with horizons from disturbed sites containing 25% less total C than horizons from the least disturbed sites. δ13C signatures of soil profiles at these sites show vertical mixing of plant-derived material into deeper mineral horizons. We propose that mixing, as a result of physical disturbance in the upper soil horizons, has led to C depletion in deep mineral soil. Regardless of the mechanism, these results suggest that increased CO2 emissions from soil may occur following harvest, and, thus, have implications for the validity of treating harvested wood biomass as a carbon neutral energy source.