PARENT SESSION
Poster Session #5: Disturbance Ecology I.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
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Influence of canopy gaps, vines, and cambial damage by deer on understory tree growth rates.
Pedersen, Brian*,1, Howard, Jessica2, Wallis, Angela1, Pears, Sarah1, 1 Environmental Studies Department, Carlisle, Pennsylvania2 Environmental Studies Program, Hamilton, New York
ABSTRACT- Because of the greater availability of light and other resources, understory trees located within or near forest canopy gaps are expected to grow faster than comparable trees located away from gaps. However, vines and cambial damage to trees by deer, which can reduce tree growth rates, may be more prevalent in gaps. Our study site is a red oak - mixed hardwood forest in south central Pennsylvania with a high density of white-tailed deer. We are comparing the stem diameter growth rates of understory trees growing at four positions: within gaps, within expanded gaps, adjacent to gaps, and in the null gap (representative of the entire forest). We rated all trees for the extent of vine influence (0-3 scale) and the extent of cambial injury likely to be from deer antler abrasion (buck rub; 0-2 scale). Based on our preliminary analysis, with growth rate measured as the combined width of the last three complete growth rings, there is no difference in the growth rates of trees at the four positions (p=0.7, analysis of covariance with stem diameter at breast height as covariate, covariate p=0.007, n=121 trees). Compared to similar-sized null gap trees, the gap, expanded gap, and gap adjacent understory trees combined were more likely to have vines (51% vs. 35%, p=0.007, Pearson chi-square test, n=327) but were not more likely to have buck rubs (23% vs. 15%, p=0.08, n=334). After accounting for tree dbh, we found no correlation between tree growth rates and the vine ratings (r=-0.09, p=0.34, n=118) or buck rub ratings (r=0.08, p=0.39, n=119). We are continuing to explore the hypothesis that the negative effects of vines and buck rubs offset the positive effect of the gap environment on understory tree growth rates.
KEY WORDS: red oak - mixed hardwood forest, tree rings, forest dynamics, invasive plants