RELATIONSHIP BETWEEN BIRDSEYE SUGAR MAPLE (ACER-SACCHARUM) OCCURRENCEAND ITS ENVIRONMENT

We tested the premise that the ''birdseye'' grain abnormality in sugar maple (Acer saccharum Marsh.) develops from local environmental condi tions, with special emphasis on the role of competition in birdseye fo rmation. Previous experience with birdseye maple frequency and the inh erent differences in stand structure between old-growth and managed no rthern hardwoods led to stratification by stand type. Old growth conta ined considerably more birdseye than managed stands, but the levels in both types exceeded previously published frequencies. Unlike earlier studies, we did not fmd greater local density (and, presumably, greate r competition) surrounding birdseye maples (versus non-birdeyes) in ei ther old-growth (31.5 and 30.9 m(2).ha(-1), respectively) or managed n orthern hardwoods (25.0 and 23.7 m(2).ha(-1), respectively). Except fo r diameter, no tree variable strongly correlated with birdseye occurre nce. Two plot-level variables, stand density and percent hemlock stems , strongly correlated with stand-level birdseye frequency primarily be cause of differences related to stand type, not because they represent ed causal factors. A logistic regression model was developed to estima te the likelihood of birdseye occurrence in an individual tree. Model performance varied, with non-birdseyes being predicted more accurately than birdseye maples. No evidence in this study explicitly supported a competition-birdseye linkage, but the frequency of birdseye in old g rowth suggests that prolonged suppression may influence birdseye forma tion from the extended exposure to a highly competitive environment. M anagement apparently results in decreased birdseye occurrence, a trend that might be ameliorated through retention of higher residual basal area and structure similar to old-growth stands.