Variations de la régénération préétablie dans les sapinières boréales en fonction de leurs caractéristiques écologiques

Abstract

The renewal of boreal fir stands after harvesting is related to the abundance of fir advanced regeneration. The objective of this study was to compare the advanced regeneration in 45-years-old balsam fir stands of second growth to determine if ecological site conditions could explain some regeneration problems noted in the balsam fir – white birch ecoclimatic domain. Seven ecological phases were studied; these are among the most common in the Laurentians north of Québec. On the basis of fir seedling densities (2 years old and more), three groups could be distinguished using a cluster analysis method for grouping means. Dry balsam fir – herb-and-moss type on well drained tills formed a first group characterized with very high seedling densities (> 60 000 seedlings/ha). A second group, characterized with high seedling densities (25 000 – 40 000 seedlings/ha), was constituted of three phases with an important moss cover:the mesic balsam fir – moss-and-herb type on moderately well drained tills, the humid balsam fir – moss-and-herb type on imperfectly drained tills with seepage, and the humid balsam fir – moss type on imperfectly drained tills. A third group, with low seedling densities (< 15 000 seedlings/ha), included three phases recognized by their important herb cover associated with a less abundant moss cover: the dry balsam fir – herb type on well drained till, the mesic balsam fir – white birch – herb type on moderately well drained till, and the mesic rich balsam fir – herb type on moderately well drained tills with seepage. Low densities of fir advanced regeneration seemed to be related to the abundance of leaf litter on the forest floor that could hinder fir regeneration. Insufficient natural coniferous regeneration can be anticipated in this last group if harvesting follows the 45-year rotation currently used now in Quebec.