Variation in Balsam Fir Needle Length Due to Crown Position, Foliage Age, and Intertree Differences

Needle length of young balsam fir ( Abies balsamea (L.) Mill.) trees increased an average of 20 percent during the first 4 years after a spacing treatment in the stand. Analysis of variance showed statistically significant differences in mean needle length between trees, and among age classes and crown positions within trees. Differences in needle length between trees within a plot were not related to tree characteristics such as dbh, height, or crown dimensions, and there was no pattern to changes in needle length with crown position in most of the trees examined. Length of different age classes of needles in trees within a plot showed a consistent pattern among trees, probably related to growing conditions during the period of shoot elongation. The large differences in mean needle length between trees and age classes suggest that care must be taken in sampling needle size, to ensure that observed differences between treatments are real. Forest Sci. 29:412-422.