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

Résumé

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