Impact des éclaircies commerciales sur la croissance et la qualité du bois de l'épinette noire (Picea mariana (Mill.) BSP) en forêt boréale /

Abstract

Ill caractéristiques des arbres résiduels et de leurs compétiteurs. Bien que l'accroissement radial observé suite au traitement soit plus important à la base de l'arbre, cela n'entraine pas de variation significative de la forme ou du défilement de la tige. Aucune variation significative du MOE et de la densité n'a été notée après le traitement. Finalement sous certaines conditions de marché, Péclaircie commerciale peut augmenter la valeur finale du peuplement par rapport à un peuplement non traité. Le "timing" de l'opération pourrait donc influencer la rentabilité des éclaircies commerciales.Mots Clés : Éclaircie commerciale, Épinette noire, qualité du bois, croissance radiale, module d'élasticité, défilement, densité de cerne, rendement, forêt boréale, défilement. IV ABSTRACTFor the last ten years the forests allocated to commercial interests have declined due land conservation, to respect the territorial claims of the First Nations and because the limits of exploitation were attained in certain regions. It is thus necessary to find strategies to increase the volume of wood produced in the remaining forests. The silvicultural practices, such as the thinning, have been effective for several decades in mixed and leafy forests in southern Quebec, but more recently have been used in a less informed way in the northern forests. The forestry companies of the region 02 (Saguenay Lac St-Jean) currently use treatments of commercial thinning in black natural spruce stands. The evaluation of the volume yield in volume remains a priority; on the other hand, the increase in radial growth caused by the thinning treatments can be associated with a decrease in mechanical wood properties. This has to be considered both during the first transformation and when evaluating the wood quality. Coniferous trees respond to increased light by producing some weaker density wood. If it turns out that thinning performed on thousands of hectares of land does not attain the industry standards in terms of mechanical resistance or depreciated quality, the impact on the market value of the wood coming from region 02 would be economically fatal. The main objectives of the thesis were to: 1) Establish radial and volume growth increment at the individual and at the stand scale using dendroecological methods. 2) Determine wood quality variations (modulus of elasticity -MOE -and ring density) before and after thinning. 3) Estimate economical returns in thinned and control stands based on recovery products available after CT and final harvest. The results suggest that commercial thinning leads to an increase of radial growth at the individual level. Response depends upon tree diameter and competition, with the biggest trees exhibiting the lowest response to the treatment.Growth increment in thinned trees appears to occur at the expense of natural radial growth in the upper part of the stem. However, no significant variation in taper or stem shape has been noticed. Moreover, no significant variation in average ring density due to CT was observed afte...

Croissance et qualité du bois de l'épinette noire et du sapin baumier après une coupe avec protection des petites tiges marchandes (CPPTM) /

“…Ainsi, les échantillons sélectionnés le plus près de l'ecorce contiennent principalement des cernes de croissance formés dans les années après la CPPTM, alors que les échantillons pris plus à l'intérieur comprennent des cernes formés avant la coupe (Vincent, 2010). De cette façon, il est possible d'effectuer séparément des tests avec du bois formé avant et après le traitement.…”