Effects of Early Pruning on Ring Specific Gravity in Young Loblolly Pine Trees

Juvenile wood is not well suited for use in many forest products. Understanding factors that affect the formation of juvenile and mature wood is important when managing commercially important conifer species. The purpose of this investigation was to determine the contribution of ring age, relative height in the stem, and crown position (within or not within the green crown) on ring specific gravity of loblolly pine trees pruned at young ages. A designed experiment consisting of five treatments, control; prune at age 3 yr, age 6 yr, or age 9 yr; and at ages 3,6, and 9 yr, was established at two locations in the Piedmont region of Virginia. Wood samples were acquired at three heights along the stem 15 yr after planting. Results showed that differences in ring specific gravity of the treated plots (Half of green crown removed at each scheduled pruning) were significantly higher than that of the control plots. All variables of ring age, relative height and ring position of within or not within the green crown, were statistically significant. The results suggest that cambial age, maturation, and proximity to green crown are important for controlling whole-ring specific gravity in loblolly pine trees. 

Modeling the impact of thinning on height development of dominant and codominant loblolly pine trees

Data collected from loblolly pine thinning study plots established in plantations on cutover, site-prepared lands were used to evaluate thinning impact on height growth of dominant and codominant loblolly pine trees. Height growth was reduced initially by thinning but was increased after 3 years following thinning. The average total height of dominant and codominant trees in thinned stands exceeded its counterpart in unthinned stands 12 years after thinning. Initial growth response to thinning was less at older stand ages than at younger ages. A model was constructed to characterize the development of height in thinned and unthinned stands. This model reflects the initial suppression of dominant and codominant height growth followed by an acceleration as a result of thinning.Modélisation de l'impact de l'éclaircie sur le développement en hauteur des arbres dominants et codominants chez Pinus taeda L. Des données récoltées dans des dispositifs expérimentaux d'étude des éclaircies, installés dans des plantations de Pinus taeda, ont été utilisées pour évaluer l'impact de l'éclaircie sur la croissance en hauteur des arbres dominants et co-dominants. La croissance en hauteur a été initialement réduite par éclaircie, mais s'est accrue dans les 3 ans suivant l'éclaircie. La moyenne de la hauteur totale des arbres dominants et codominants dans les peuplements éclaircis est supérieure à celle des arbres dominants et codominants des peuplements non éclaircis, 12 ans après l'éclaircie. La réponse initiale en termes de croissance à l'éclaircie était plus faible dans les vieux peuplements que dans les peuplements jeunes. Un modèle a été construit pour caractériser l'évolution de la croissance en hauteur dans les peuplements éclaircis et les peuplements non éclaircis. Ce modèle reflète l'effet initial dépressif de l'éclaircie sur la croissance des arbres dominants et codominants suivi d'une accélération comme résultat de l'effet d'éclaircie