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Harvard Forest Symposium Abstract 2010

  • Title: Post-Disturbance Carbon, Water, and Energy Exchanges in an Early Succession New England Landscape
  • Primary Author: Christopher Williams (Clark University)
  • Additional Authors: Emery Boose (Harvard Forest); Julian Hadley (Harvard Forest); J. William Munger (Harvard University); Mark VanScoy (Harvard Forest)
  • Abstract:

    Forest disturbances are known to perturb ecosystem-atmosphere exchanges of water, carbon, and energy in profound ways. However, the degree, character, and persistence of such perturbations are largely unknown. How rapidly is post-disturbance slash decomposed and emitted to the atmosphere? How long does it take for plant productivity to recover so that a disturbed site crosses over from a net source to a net sink? How do disturbance-induced changes in albedo, surface temperature, and evapotranspiration combine to influence atmospheric warming/cooling?

    In summer 2009 we deployed a low stature eddy covariance tower in a harvested plot on top of Prospect Hill to address these questions with semi-continuous measurements of land-atmosphere exchanges of heat, moisture, carbon dioxide, and momentum as well as associated environmental conditions. Results from the “Cut” site are compared to simultaneous measurements at the nearby Environmental Monitoring Station (EMS). We find broad consistency with heuristic and pedagogical expectations.

    In the early summer the cut site had sizeable CO2 emissions and near zero midday uptake, consistent with the extensive cover of decomposing slash and a largely unvegetated condition that persisted until the middle of July. Evapotranspiration (ET) was lower in the clearcut and the difference increased through the summer despite an expanding ground cover of ferns, vines, and some sumac. Low ET was most likely due to low leaf and root areas but may have also derived from less available energy at the clearcut site associated with higher shortwave albedo and elevated longwave emission. The clearcut experienced only slight daily net carbon uptake by mid-August despite significant midday photosynthetic activity. Even so, throughout the growing season plant productivity remained far below that measured at the EMS tower.

  • Research Category: Forest-Atmosphere Exchange
    Physiological Ecology, Population Dynamics, and Species Interactions