Abstract
This paper discusses the impact of competing vegetation on balsam fir (Abiesbalsamea (L.) Mill.) seedling growth. The study consisted of 12 permanent sample blocks of 0.5 ha. In each one, about 60 seedlings were selected to represent the various levels of competition. Ten competition indices were computed and compared for their relationship with balsam fir growth in height and diameter. Growth was slightly reduced by the competing vegetation but the relative production rate was not affected. An index using competing vegetation density and height relative to the seedling was selected for its simplicity and good correlation with the growth parameters. A simulation indicates that height growth for the next 5 years should remain correlated, although weakly, with the competing vegetation abundance. Balsam fir would be able to quickly overtop raspberry but would remain in the understory for some time when overtopped by hardwood light demanders.