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Harvard Forest REU Symposium Abstract 2006

  • Title: Aboveground Woody Detrital Biomass Decreases and Respiration Increases in the 5 Years Following Selective Harvest
  • Author: ()
  • Abstract:

    Coarse woody debris (CWD; diameter≥7.5cm) accounts for as much as 30% of net ecosystem exchange in the maturing second growth forests partially responsible for terrestrial carbon(C) uptake in North America. We investigated changes in aboveground woody debris (WD) once before, and three times following a 2001 selective harvest. We inventoried CWD dimensions on 33 Environmental Measurement Site (EMS; control) plots and on 8 adjacent selectively harvested (cut) plots at Harvard Forest. We calculated CWD C content using decay class specific wood densities and dimension derived volumes. CWD biomass at the cut plots increased after the harvest, but has nearly decreased to pre-harvest levels by 2006. The cut site volume remained static from 1999 through 2006. After the harvest in 2001, the volume in less decay classes increased, while the volume in more decayed classes decreased. Between and 2001 and 2006, the distribution of decay classes at the cut site has approached pre-harvest levels, however, there is still more volume in less decayed classes. The control site had less initial WD volume and biomass. The control pool has consistently increased in volume and biomass in all survey years. We used a linear regression model to estimate CWD respiration for 2003 through 2006 based on decay class biomass and site-specific hourly air temperatures. At both sites the estimated CWD pool was larger than the measured pool in 2006. Fragmentation and leaching accounts for this difference. The larger difference at the control site suggests more fragmentation and leaching. CWD respiration was higher at the cut site than at the control site, but increased from year to year at both sites. Selective harvest related changes in WD pool dynamics have important implications for forest management and global C dynamics.

  • Research Category: Forest-Atmosphere Exchange