The objective of this paper was to investigate the impact of initial spacing and pre-commercial thinning (PCT) on tree growth, characteristics and stem quality in plantation-grown jack pine (Pinus banksiana Lamb.) after 58 years of growth. Four spacings including three initial spacings without PCT treatment, i.e., 1.52 ϫ 1.52 m (5 ϫ 5 ft), 2.13 ϫ 2.13 m (7 ϫ 7 ft) and 2.74 ϫ 2.74 m (9 ϫ 9 ft) and one initial spacing with PCT treatment (5 ϫ 5 ft thinned to 7 ϫ 7 ft at age 14), were chosen to analyze diameter at breast height (DBH) distribution, survival, and various tree and stem quality characteristics (e.g., DBH, total tree height, stem volume, crown size, branch, taper, sweep and wobbling). Tree mortality during the first 25 growth years was quite low for all four spacings, while after 25 years, survival for the four spacings rapidly declined. The decrease in survival for spacing 5 ϫ 5 was the steepest, followed by spacings 7 ϫ 7, 9 ϫ 9 and finally the PCT-treated stand. DBH distributions for all four spacings were significantly different from each other, and five years after PCT, the 5 ϫ 5 to 7 ϫ 7 spacings had a similar DBH distribution to that of the constant 7 ϫ 7 spacing. Mean DBHs differed significantly among the initial spacings. The 5 ϫ 5 spacing produced significantly smaller trees than did the other three spacings through the years, and the 9 ϫ 9 spacing produced significantly larger trees. PCT had positive effects on DBH growth, and yielded longer merchantable stems and better stem quality. PCT had little effect on crown development. Initial spacing significantly affected diameter growth, crown width and branch development, commercial stem length and volume, stem taper and stem deformation. Narrower spacing produced smaller but better quality stems. Spacing 7 ϫ 7 had the worst stem quality in terms of overall sweep and wave-like transversal deformation (wobbling). A narrow initial spacing followed by a PCT treatment may provide a compromise solution for both tree growth and stem quality.
Precommercial thinning (PCT) is often used to improve stand growth and value. While PCT may accelerate tree growth and reduce mortality, it may also have a negative effect on product quality. This study examined the effect of moderate and heavy thinning on tree growth, lumber recovery and quality in a natural balsam fir [Abies balsamea (L.) Mill.] PCT trial 35 years after thinning. Compared with the control, the heavy thinning increased merchantable tree diameter, stem volume per tree and lumber volume recovery per tree by 41.1%, 100.9% and 92.7%, respectively, reduced the Select Structural grade (the best grade) recovery by 33.7%. Thinning did not affect the no. 2 and better grade yield. There was a 12.2% and 15.0% difference, respectively, in the lumber bending modulus of elasticity (MOE) and modulus of rupture (MOR) between the control and heavy thinning. Moderate thinning had little impact on the visual grade recovery, lumber bending MOE and MOR. Heavy thinning is recommended if the goal is to get sizeable sawlogs in the shortest time, whereas moderate thinning is preferable if the intention is to minimize the negative effects on lumber quality while retaining modest tree growth and lumber recovery. Overall, PCT of very dense young balsam fir stands appears to be an effective and viable silvicultural treatment.
-End uses and product recovery are important considerations in forest management decision-making. This study intended to develop general tree-level lumber volume recovery models for jack pine. A sample of 154 jack pine trees collected from natural stands was scanned to obtain 3-D stem geometry for sawing simulation under two sawmill layouts, a stud mill and a random mill with optimized bucking, using sawing simulator Optitek. Three model forms were chosen to describe the quantitative relationship between simulated lumber volume recovery and tree characteristics. It was found that lumber volume recovery of individual trees from both sawmills could be well estimated from DBH using a second-order polynomial equation. Adding tree height into the model resulted in a small but significant improvement in the goodness of the model. Adding tree taper into the model that already included DBH and tree height no longer improved the goodness significantly. The power function form involving only DBH or both DBH and tree height as variables was also found to be suitable for the stud mill; exponential forms were least suitable. The second-order polynomial model with DBH alone was the most suitable model when inventory records DBH only, while the second-order polynomial model and the power model involving two variables (DBH and tree height) for the random mill and the stud mill, respectively, were better when both DBH and tree height are available.tree characteristics / sawing simulation / Optitek / lumber recovery / general model Résumé -Modélisation du rendement en sciages en relation avec certaines caractéristiques du pin baumier en utilisant le logiciel de simulation Optitek. L'utilisation finale et le rendement en produits sont des considérations importantes dans la prise de décision en aménagement forestier. Cette étude vise à développer des modèles généraux de rendement en volume au niveau de l'arbre du pin baumier. Un échantillon de 154 arbres de sapin baumier récoltés dans des peuplements naturels a été scanné pour obtenir la géométrie 3-D des tiges pour effectuer la simulation selon deux configurations d'usine, soit une scierie de bois de colombage et une usine variable avec tronçonnage optimisé avec le simulateur de sciage Optitek. Trois formes de modèles ont été choisies pour décrire la relation quantitative entre le rendement en sciage simulé et les caractéristiques de l'arbre. Il semble que le rendement en sciage d'arbres individuels provenant des deux scieries peut être bien estimé à partir du DHP en utilisant une équation polynomiale de deuxième ordre. L'ajout de la hauteur de l'arbre aux résultats du modèle est une petite amélioration, mais tout de même significative pour la validité du modèle. Toutefois, l'ajout du défilement de l'arbre à un modèle incluant déjà le DHP et la hauteur de l'arbre n'améliore pas significativement la validité. Les équations de fonction puissance impliquant seulement le DHP ou le DHP et la hauteur de l'arbre comme variables se sont avérées appropriées pour l'usine de colomba...
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