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Harvard Forest Symposium Abstract 2013

• Title: Post-clearcut dynamics of carbon, water and energy exchanges in a mid-latitude, temperate forest environment
• Primary Author: Christopher Williams (Clark University)
• Additional Authors: Myroslava Khomik (Clark University); Melanie Vanderhoof (Clark University)
• Abstract:

  Clearcutting and other forest disturbances perturb carbon, water, and energy balances in significant ways, with corresponding influences on Earth’s climate system through biogeochemical and biogeophysical effects. However few observations are available to quantify the precise changes in these balances following disturbances of different types, severities, and in various climate and ecosystem type settings. This study combines eddy covariance and micrometeorological measurements of surface-atmosphere exchanges with vegetation inventories and chamber-based estimates of soil respiration to quantify how carbon, water, and energy fluxes changed during the first three years following forest clearing in a temperate forest environment of New England. We observed rapid recovery with sustained increases in gross ecosystem productivity (GEP) over the first three growing seasons post-clearing, coincident with large and relatively stable net emission of CO2 because of overwhelmingly large ecosystem respiration. The rise in GEP was attributed to vegetation changes not environmental conditions (e.g. weather), but attribution to the expansion of leaf area versus changes in vegetation composition remains unclear. Soil respiration was estimated to contribute 44% of total ecosystem respiration during summer months and coarse woody debris accounted for another 18%. Evapotranspiration also recovered rapidly and continued to rise across years with a corresponding decrease in sensible heat flux. Gross shortwave and longwave radiative fluxes were stable across years except for strong wintertime dependence on snow covered conditions and corresponding variation in albedo. Overall, these findings underscore the highly dynamic nature of carbon and water exchanges and vegetation composition during the regrowth following a severe forest disturbance, and sheds light on both the magnitude of such changes and the underlying mechanisms with a unique example from a mid-latitude temperate forest.

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