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Harvard Forest Symposium Abstract 2013

• Title: The Importance of Age, Competition and Succession in Acer rubrum Decline in a Northeastern Mixed Deciduous Forest
• Primary Author: Fiona Jevon (Dartmouth College)
• Abstract:

  The Importance of Age, Competition and Succession in Acer rubrum Decline in a Northeastern Mixed Deciduous Forest
  
  Fiona Jevon
  
  Senior Thesis advised by William Munger and Andrew Richardson
  
  
  
  Abstract
  
  Acer rubrum (red maple) and Quercus rubra (red oak) dominate many northeastern deciduous forests, including the Harvard Forest in Petersham, MA. These species have distinct ecological characteristics: red maples are an opportunistic, shade tolerant, relatively short-lived species, while red oaks are less shade tolerant, but live longer (Abrams and Kubiske, 1990; Lichtenthaler et al, 1981; Loach, 1970, Walters and Reich, 1996). The classical literature on succession suggests that over time red maples will therefore increase their dominance in mixed red oak-red maple stands (Abrams, 1998; Hibbs, 1983; Lorimer, 1984). However, data collected at the Harvard Forest has documented an apparent decline in the growth rate of red maples (Pederson, 2005). I hypothesized that this decline is due either to the species-specific life expectancy, or to competitive pressure exerted on the red maples, particularly by increasingly dominant red oaks. In order to investigate these hypotheses at both the individual and site level, I collected data on the size and distance between red maples and their competitors at three different sites at the Harvard Forest: a “control” site, an “open” site, and a “young” site. Additionally, I collected cores from these trees in order to determine age and long-term growth rates, and analyzed the available data on understory composition and tree mortality. I found that there was a weak positive correlation between red maple growth rate and age, suggesting that red maple growth is not limited by age. There was no significant correlation in red oaks. I also found that individual red maple growth rates are significantly limited by their level of competitive stress. Disturbance events release red maples from this competition, resulting in increased growth. In spite of the decline in the canopy, the understory is overwhelmingly dominated by red maple. This suggests that although individual red maples are declining or dying, it is unlikely that a large shift in species composition will occur at the site level. In fact, the interaction between red maple and red oak may result in a stable ecosystem.
  
  

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