ALTERNATIVE MEASURES OF STEM GROWTH EFFICIENCY APPLIED TO ABIES-BALSAMEA FROM 4 CANOPY POSITIONS IN CENTRAL MAINE, USA

Stem analysis data collected from 39 Abies balsamea (L.) Miller from f our distinct canopy positions (open-grown, codominant, intermediate, s uppressed) were used to construct a model to predict stem volume incre ment (VINC) from projected leaf area (PLA), and test the hypotheses th at the physiological-based measure for growth efficiency (GE, stem vol ume increment per leaf area) and the empirical surrogates for GE (e.g. surrogates substituting other measures of stem volume increment or PL A into the GE equation) were equal among canopy positions, VINC was be st predicted from PLA with an asymptotic model which suggests that onc e individual trees reach a critical leaf area, very little stem growth occurs relative to leaf area. Analyses of variance revealed that the suppressed crown class was the least efficient (in terms of GE or any of its surrogates) relative to the superior canopy positions, Observed and predicted patterns of growth efficiency were found to depend on t he manner in which it was calculated or predicted. Suppressed trees, h owever, were consistently observed, and predicted to be the least effi cient in terms of stem volume increment relative to the intermediate, codominant, and open-grown crown classes.