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Harvard Forest Symposium Abstract 2013

  • Title: Forest Dynamics in Former Plantations at the Harvard Forest
  • Primary Author: Audrey Barker Plotkin (Harvard Forest)
  • Additional Authors: Anne Cervas (Harvard College (Harvard University))
  • Abstract:

    During the early years of forestry in southern New England, plantations played a key role in afforestation of open lands and building a regional wood supply. Plantations at the Harvard Forest were established from 1911-1944. The total acreage planted came to nearly 400 acres (16% of Harvard Forest’s land base in 1935). In 2001, the Harvard Forest began planning how to bring nearly a century of plantation research to a grand finale, and developed a management plan in which 80 of the remaining 125 acres of plantations were harvested, with 85-100% canopy removal. In 2007, we established a suite of permanent plots in plantations that were subsequently harvested (2008-2009) or left as controls. In 2012, we resampled the plots to examine changes in vegetation biodiversity and structure over five years. We were particularly interested to investigate variation in response between the harvested and control plots, variation in response among the harvested plots, and whether the control sites are shifting toward native forest without harvesting.



    The sites are grouped by plantation type (8 pine, 4 spruce) and treatment (6 harvest, 6 control). The larger sites include more than one plot; there are a total of 22 plots, each 20m by 20m. Vegetation composition and structure was assessed by measuring trees (diameter >2.5cm), tree regeneration (stems >1.3m tall but <2.5cm diameter), tree seedling stocking, vascular plant species richness and cover, and dead wood volume. Data from sites with multiple plots were averaged prior to analysis.



    As expected, overstory basal area in the harvested plots was very low (0-8m2/ha) three to four years post-harvest (Figure 1a). More surprising was the finding that basal area did not increase in the control plots; in fact, most control sites lost basal area (a two-way ANOVA showed that time, treatment, and time x treatment were all significant, ie., p<0.05). Volume of downed dead wood increased with decreasing basal area (Figure 1b). All sites are well-stocked with a variety of tree seedlings, and sapling densities showed a notable but non-significant increase from 2007-2012 in most of the harvested sites and one control site (Figure 1c). Plantation species (Pinus resinosa, Picea abies and Picea glauca) comprised no more than 10% of the seedling and sapling regeneration at any site. Understory species richness and cover showed modest, but non-significant, increases after harvest (Figure 1d). Of five woody invasive plant species observed in 2012, four were found only in harvested plots.



    The plantations of Harvard Forest are moving toward mixtures of native tree species. Harvesting hastens this transition; however, the control sites are either static or losing basal area, in contrast with the aggrading native forests at Harvard Forest and central New England (e.g. Thompson et al. 2011, Urbanski et al. 2007). Harvested plantations may be at higher risk for invasion by non-native shrubs, but this is not clearly a function of harvesting activity. Whether with a bang or a whimper, the plantation era of Harvard Forest is coming to an end. We will continue to study the dynamics and variability in these sites as they transition to naturally regenerated forest.



    References cited

    Thompson, J. R., Foster, D. R., Scheller, R., Kittredge, D. B. 2011. The influence of land use and climate change on forest biomass and composition in Massachusetts, USA. Ecological Applications 21: 2425-2444.



    Urbanski, S. P., Barford, C. C., Wofsy, S. C., Kucharik, C. J., Pyle, E. H., Budney, J., McKain, K., Fitzjarrald, D. R., Czikowsky, M. J., Munger, J. W. 2007. Factors controlling CO2 exchange on time scales from hourly to decadal at Harvard Forest. Journal of Geophysical Research - Biogeosciences 112.

  • Research Category: Biodiversity Studies
    Conservation and Management
    Large Experiments and Permanent Plot Studies

  • Figures:
  • C:dataplantation-researchBarkerPlotkinFig1.pdf