Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

Defoliation by spruce budworm (Choristoneura fumiferana Clem.) greatly affects balsam fir (Abies balsamea (L.) Mill.) by reducing needle mass and ring width and eventually resulting in tree death. We analyzed temporal patterns of radial growth in various stem sections of twenty balsam fir growing in two mature stands, one intermediate-aged, and one immature stand in New Brunswick, Canada. Growth was compared to annual defoliation data from aerial surveys to determine the timing of growth reduction throughout the stem. Results indicated that there was a delay between the first radial growth reduction registered in the crown and reduction in the lower part of the stem. The delay was variable, depending upon stand age. In immature trees, ring width reduction occurred almost simultaneously along the entire stem, whereas in mature fir, the growth reduction occurred one to three years earlier in the crown than at the stem base. In mature trees, the reduction in the crown occurred immediately in the first year following severe defoliation (70-100% of current year foliage), whereas in severely defoliated immature trees, growth reduction occurred 1 to 2 years later.