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Harvard Forest Symposium Abstract 2007

  • Title: Harvard Forest Hurricane Experiment: Changes in Tree Composition and Structure
  • Primary Author: Audrey Barker Plotkin (Harvard Forest)
  • Additional Authors: David Foster (Harvard University); Brynne Simmons (Johnson C Smith University)
  • Abstract:

    The hurricane experiment at Harvard Forest was designed to simulate the impacts of a catastrophic storm like the 1938 New England Hurricane to mature red oak – red maple forest. In October 1990, canopy trees were pulled over using a winch, resulting in direct and indirect damage to nearly 70% of the stand. Despite massive structural reorganization, the site maintained biogeochemical function and resisted major change in understory species composition. This contrasts with the more dramatic changes seen after the 1938 hurricane, where hurricane effects were conditioned by a landscape dominated by old-field white pine, and the region-wide salvage logging that followed this hurricane (Foster et al. 2004).



    One goal of the experiment is to examine long-term changes in tree species composition and structure. In summers 2000, 2003 and 2006, we surveyed all stems that had grown above 5 cm dbh (diameter at breast height) across the experimental and control sites. These new recruits to the stand represent the most vigorous fraction of the total regeneration at the site, and suggest how the future composition of the forest will differ from the pre-manipulation stand.



    Between 2000 and 2006, the number and basal area of new stems >5 cm dbh increased in the experimental site (Table 1). In the unmanipulated control site, stem density and basal area also increased between 2000 and 2006, but the totals were very low. Species composition of the recruits was similar in all years sampled.



    The new cohort in the manipulation is dominated by black birch (Betula lenta), followed by red maple (Acer rubrum) and yellow birch (Betula alleghaniensis). Early successional species such as paper birch (Betula papyrifera) and pin cherry (Prunus pensylvanica) form a relatively minor component of the new cohort, and are mostly found on localized areas of soil disturbance such as tip-up mounds. Red oak (Quercus rubra) was a dominant species in the pre-manipulation forest, but only two red oaks have grown into the 5 cm size class since 1990. However, legacy trees from the pre-disturbance forest continue to dominate basal area; for example, the few remaining undamaged red oaks tower over the developing canopy and contribute 40% of the 2005 basal area in the experimental site (Figure 1a). The experimental site has a heterogenous height and age structure, (Figure1a,b) and while species composition has shifted more than in the control site (Figure 1c, bottom panel), these changes are moderated by undamaged and rebuilding stems from the original stand.





    Foster, D.R., S. Cooper-Ellis, A. Barker Plotkin, G. Carlton, R. Bowden, A. Magill and J. Aber. 2004. Simulating a catastrophic hurricane. Pages 235-258 in Foster, D.R. and J. D. Aber (eds.). Forests in Time: The Environmental Consequences of 1,000 Years of Change in New England. Yale University Press, New Haven, CT.

  • Research Category: Historical and Retrospective Studies
    Large Experiments and Permanent Plot Studies

  • Figures:
  • C:data omswampgeneralTable1-abp-hurricane.pdf
    C:data omswamp reeFigure1-abp-hurricane.pdf