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Harvard Forest REU Symposium Abstract 2007

  • Title: Dead Wood in the Forest Ecosystem: An Ongoing Study of the Effects of Eastern Hemlock Removal
  • Author: Jan Ng (Harvard University)
  • Abstract:

    Widespread decline of eastern hemlock (Tsuga canadensis) as a foundation species in northeastern forests is set to have a pervasive impact on this landscape, but distinct effects on the forest ecosystem are as yet unknown. The Hemlock Manipulation Study contrasts hemlock removal by Adelges tsugae infestation (simulated by girdling) and preemptive logging treatments with hemlock and hardwood control plots. The coarse wood debris (CWD) survey within this study analyzes dead wood dynamics in the ecosystem. The 2007 survey represents a continuation of data collected post-treatment in 2005.



    Dead wood mass was assessed in eight 0.8 ha forest plots along transects (coarse and fine downed dead wood) and strip plots (standing dead wood). Species, size, and decay class were noted for all surveyed material.



    Girdled plots were found to contain the greatest amount dead wood, more than 85% of which (by mass) came from standing snags and stumps. In logged plots, ≈18,000 kg/ha of downed dead wood had shifted from decay class 1 (least decayed) to decay classes 2 and 3 between the 2005 and 2007 surveys. Girdled plots currently have ≈122,000 kg/ha more standing dead eastern hemlocks than hemlock control plots, whereas in 2005 the masses differed by less than 1,000 kg/ha. Large snags (pieces standing ≥2m tall and measuring ≥25cm in base diameter) comprised over 110,000 kg/ha of the ≈126,000 kg/ha total dead wood mass in girdled plots. By comparison, less than 2,000 kg/ha out of ≈8,500 kg/ha standing dead wood in logged plots, ≈13,500 kg/ha out of 14,000 kg/ha in hemlock control plots, and 2,500 kg/ha out of 8,500 kg/ha in hardwood control plots were large snags.



    These data, upon integration with other surveys in the experiment, may clarify the impact that inputting large quantities of dead T.canadensis will have on northeastern forest ecosystem structure, habitat, and nutrient dynamics.

  • Research Category: Large Experiments and Permanent Plot Studies