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& Key Message Wood properties were generally similar in unmanaged even-aged and uneven-aged black spruce stands. In contrast, in managed forests, wood density was higher in even-aged than in uneven-aged stands. As ring width is the discriminant factor, forest management should regulate the intensity of partial cutting to maintain a high wood density. & Context North American boreal forests experience recurrent disturbances, such as fire and insect outbreaks, that shape the structure of even-aged and uneven-aged stands. Ecosystem-based forest management practices, such as partial cutting, aim to increase timber yields, and these forest harvesting approaches are being applied more frequently. Although the influence of these practices on tree growth is well known, few studies have examined their impact on anatomy and density of the resulting wood. & Aim This research studied the relationships between wood properties and ring width and tree heights in even-and uneven-aged black spruce (Picea mariana (Mill.) BSP) stands and how these relationships are modified following partial cutting. & Method Wood density (ring, earlywood, latewood, and maximum density) and anatomical traits (lumen area, cell-wall thickness, and tracheid length) were measured at breast height on the stem of black spruce trees. The measured wood properties were then correlated with ring width and stem height. & Results The model demonstrated significant correlations between most measured wood parameters and ring width with only small differences between even-and uneven-aged unmanaged stands. Five wood properties were influenced by tree height in even-aged and uneven-aged unmanaged plots. Partial cutting increased the number of significant relationships between wood properties (ring, latewood, maximum density, early-and latewood lumen area, tracheid length) and tree height. We detected differences in wood properties between even-and uneven-aged plots. Although we detected no change in average ring density, the variation of intra-annual density increased, due to changes in earlywood and latewood density that resulted in more heterogeneous rings. & Conclusion Partial cutting should take into consideration the age structure of the stand when the density of wood products matters. Keywords Wood properties. Managed and unmanaged forest. Even-and uneven-aged forest. Picea mariana. Wood density. Wood anatomy

Branch diameter is an important aspect of wood quality, as lumber grades can be determined based on the maximum diameter of branches. Crown and branch development can be influenced by the environment surrounding the trees, and silvicultural interventions, which reduce stand density and increase the growth of residual trees, could therefore alter branch properties. We evaluated maximum branch diameter within the crown of residual black spruce (Picea mariana (Mill.) B.S.P.) subjected to five types of silvicultural intervention-three partial-cutting and two clearcutting treatments-as well as trees within unmanaged control stands. We sampled a total of 41 stands and 223 trees. We collected 15 whorls from the live crown of each tree and measured the diameters of the largest branches. For all treatments, we observed a curvilinear relationship between maximum branch diameter and distance from the stem apex, and the largest branches were located in the lower third of the live crown. DBH before treatment and treatment were the variables that best explained maximum branch diameter in the lowest portion of the crown. A generalized additive model showed that maximum branch diameter in black spruce following silvicultural treatment will not differ significantly from trees of unmanaged control stands. Therefore, the studied partial cutting and clearcutting treatments do not have adverse effects on maximum branch diameter when compared to unmanaged control stands. However, DBH prior to treatment must be considered before any treatment is applied in forest management operations if maximum branch diameter is an important wood quality factor at the time of the final harvest of the stands.

REMERCIEMENTSJe remercie également ma famille, en particulier ma mère, Diane Pamerleau, qui, grâce à son soutien, ses conseils, et sa précieuse aide dans la rédaction de ce mémoire, m'a permis de compléter cette étape importante.