Résumé - CAFD

The regeneration of balsam fir stands in their northern abundance limit is more related to their seed sources and soil types than the climate.

Yassine Messaoud, Venceslas-Claude Goudiaby, Yves Bergeron.

To explain the transition between the southern mixedwood and the northern coniferous bioclimatic domains respectively dominated by balsam fir and black spruce, 59 sample plots were selected throughout the two bioclimatic domains. The regeneration (seedling abundance) and mortality (difference between seedlings and saplings) of balsam fir seedlings were compared within and between the two bioclimatic domains. We also determined the soil types (clay and till), summer growing degree-days above 5°C (GDD_5), and total summer precipitation (PP_MA). Balsam fir regeneration was strongly linked with parental trees and was higher in the mixedwood than in the coniferous bioclimatic domain, with higher regeneration occurring on till than on clay soils. Also, the mortality was higher on till than on clay soils, due to increasing competition on tills where the regeneration is higher. Unlike PP_MA, GDD_5 positively influenced balsam fir regeneration. The dynamic of balsam fir stands in the coniferous bioclimatic domain was attributed to a decrease of balsam fir regeneration and increase of its mortality most likely due to a lack of good establishment substrates (till soils), and cooler temperatures. However, balsam fir stands persist above this northern limit prospected, owing to patchy occurrences of good establishment substrates where parental trees are found.