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Harvard Forest Symposium Abstract 2015

  • Title: Radiative Forcings from Albedo and Carbon Dynamics After Disturbance in Massachusetts Forests
  • Primary Author: Richard MacLean (Clark University)
  • Additional Authors: Christopher Williams (Clark University)
  • Abstract:

    Recent efforts have sought to compare and contrast the radiative forcings excited by forest disturbances due to both biogeochemical and biogeophysical mechanisms using either in situ measurements or modeling. Study of boreal forest disturbances led to the important finding that the albedo increase from snow exposure after a canopy destroying fire offsets the warming from carbon emissions. Similar study is lacking for temperate forests, leading to uncertainty of the net effect of albedo and carbon forcings following their disturbance. This work quantifies the gross and net radiative forcings from albedo and carbon mechanisms at a 2008 clear-cut site in Harvard Forest, Massachusetts. In 2009 an eddy flux covariance tower was established at the 2008 clear-cut on Prospect Hill (FTC). The tower provides a nearly continuous record of albedo measured with a four channel net radiometer, which was then compared to similar albedo measurements at a mature forest site, the EMS tower record. Patterns in albedo correlate well between the two towers, but the clear-cut demonstrates higher albedo throughout the year, and is especially brighter after snowfall. Carbon fluxes are estimated from modeled C release and sequestration. Associated radiative forcing is estimated with conventional methods estimating the perturbation to CO2 in the atmosphere and its lifetime considering ocean uptake (pulse response), removed timber product decay and vegetation regrowth. Albedo change beyond the span of overlap between the two towers was assessed with Landsat derived albedo at a 1990 clear-cut located near Shaler Hall (JOK). Initially albedo related radiative forcing is much greater than the C release radiative forcing resulting in a net cooling effect on the atmosphere the first three years (FTC record) after clear cut. The albedo RF appears to then diminish toward zero by 19 years after clear cut (JOK).

  • Research Category: Forest-Atmosphere Exchange