Balsam fir (Abies balsamea) establishment dynamics during a spruce budworm(Choristoneura fumiferana) outbreak: an evaluation of the impact of aging techniques

The effects of recurrent spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks on balsam fir (Abies balsamea (L.) Mill.) mortality have been ext ensively studied in Canada. Most studies report substantial seedling recrui tment of balsam fir during outbreaks when reproductive trees are dying. Acc ording to previous research, this contradiction could be due to inaccuracie s in the conventional aging method. Counting the maximum number of growth r ings found at the tree base would significantly underestimate tree age. Cou nting terminal bud scars found on the entire trunk, including buried stem, would give a more accurate tree age. In this study, we compare recruitment dynamics obtained for aging seedlings in two balsam fir populations (about 500 km apart) using (i) the conventional method and (ii) bud scar counts. F or both populations, the conventional method shows substantial recruitment during adult mortality, while the second aging technique reveals reduced re cruitment during the epidemic phase of the spruce budworm outbreak.