PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Canopy tree competition along environmental gradients in southern New England forests.
Papaik, Michael*,, Canham, Charles,
ABSTRACT- We use U.S.D.A. Forest Service Forest Inventory and Analysis (FIA) data to analyze the effects of competition on tree growth along environmental gradients for eight of the most common tree species in southern New England and southeastern New York. We evaluate 54 models that estimate growth of individual trees as a species-specific function of average potential radial growth and three factors that quantify the effects on growth of (1) initial target tree DBH, (2) local environmental conditions, and (3) neighborhood crowding. The crowding function estimates, in part, the strength of conspecific and interspecific competitive effects of neighbors. Environmental conditions are estimated with an ordination of the variation in the relative basal area of species among plots. We use information theoretic methods and multi-model inference to determine the relative weight of evidence for each model. Given the complexity of ecological systems, it is perfectly reasonable that several models could do approximately equally good jobs in explaining the information in the data. The relative weight of evidence of the best model for each species ranged from 0.207 to 0.747. The number of alternate models for which there was reasonable support in the data ranged from 3 to 13. Model averaging provides a more robust platform for prediction than prediction based solely on the "best" model. Our results indicated that predictions based on the selected best model dramatically overestimated differences between species relative to predictions based on the model-averaged set of models. The complexity of competitive interactions and performance along environmental gradients among these species and the importance of including information in alternate models via model averaging highlight key challenges for the management of mixed-species, uneven-aged stands.
Key words: multi-model inference, competition, niche theory, forest community