Modeling thinning effects on ring width distribution in loblolly pine (Pinus taeda)

Abstract

Measurements were made on loblolly pine (Pinus taeda L.) from permanent sample plots to study the effects of thinning on ring width distribution and to develop a ring width prediction model. Thinning significantly increased ring width over most of the tree bole, and its effects tended to persist over the 12 years since thinning. Significant regional variation in average ring width was evident, with average ring width tending to decrease from the Highlands, to the Coastal Plain, to the Piedmont. A ring width prediction model that accounts for position in tree, tree size, stand, and site factors as well as thinning effects was developed. While ring width showed considerable variation within trees and among trees, the model predicted a substantial portion of the variation in ring width. The model can be used to obtain reasonably good volume estimates in individual growth rings, thus enabling the direct evaluation of the effects of silvicultural treatments on volume production. The data used in this study consisted of correlated observations; hence, direct covariance modeling was used to address biases in the standard error of estimates and hypothesis tests.Résumé : Des mesures ont été effectuées sur des pins à encen (Pinus taeda L.) dans des parcelles permanentes pour étudier les effets de l'éclaircie sur la distribution de la largeur des cernes et pour développer un modèle de prédiction de la largeur des cernes. L'éclaircie a significativement augmenté la largeur des cernes presque partout dans la tige et ses effets avaient tendance à persister pendant les 12 ans après l'éclaircie. Il y avait des variations régionales importantes et évidentes dans la largeur moyenne des cernes qui avaient tendance à diminuer en passant des hauts plateaux à la plaine côtière et au piedmont. Le modèle de prédiction de la largeur des cernes qui a été développé tient compte de la position dans l'arbre, de la taille de l'arbre, des caractéristiques du peuplement et du site ainsi que des effets de l'éclaircie. Bien que la largeur des cernes variait considérablement dans le même arbre et d'un arbre à l'autre, le modèle a prédit une partie importante de la variation dans la largeur des cernes. On peut utiliser le modèle pour obtenir une estimation raisonnablement précise du volume individuellement dans chaque cerne, ce qui permet d'évaluer directement les effets des traitements sylvicoles sur l'accroissement en volume. Les données utilisées dans cette étude provenaient d'observations corrélées; la modélisation basée sur la covariance directe a donc été utilisée pour corriger les biais dans l'erreur standard des estimées et les tests d'hypothèse.[Traduit par la Rédaction]

Effects of early thinning regime and tree status on the radial growth and wood density of Scots pine

“…In a stand, the dominant and co-dominant trees have usually a higher growth rate and more tapered stems than suppressed or intermediate trees, irrespective of stand density and site fertility (Larson 1963, Kozlowski 1971, Tasissa and Burkhart 1997. Similarly, after a moderate or heavy thinning, and especially if the thinning is done at an early enough stage of stand development, these dominant and co-dominant trees also show higher absolute thinning response compared to suppressed ones because of their improved growing conditions (Ruha and Varmola 1997, Pukkala et al 1998, Peltola et al 2002, Mäkinen and Isomäki 2004a.…”

“…The magnitude of how management, such as thinning, affects the properties of wood in tree stands, depends on thinning intensity and its type, tree species, the status of the tree in a stand and whether juvenile or mature wood is being formed (Olesen 1977, Kärkkäinen 1984, Moschler et al 1989, Tasissa and Burkhart 1997, Pape 1999a,b, Mörling 2002. In general, the radial growth and the proportion of early wood of conifers has been suggested to increase with increasing growth, whereas wood density, proportion of late wood and fibre length has been suggested to decrease (Hakkila 1966, Persson 1975, Olesen 1977, Zobel and van Buijtenen 1989, Barbour et al 1994, Lindström 1996, Zhang et al 1996, Tasissa and Burkhart 1997, Pape 1999a,b, Mäkinen et al 2002.…”

“…In general, the radial growth and the proportion of early wood of conifers has been suggested to increase with increasing growth, whereas wood density, proportion of late wood and fibre length has been suggested to decrease (Hakkila 1966, Persson 1975, Olesen 1977, Zobel and van Buijtenen 1989, Barbour et al 1994, Lindström 1996, Zhang et al 1996, Tasissa and Burkhart 1997, Pape 1999a,b, Mäkinen et al 2002. Increased growth rate has been found to decrease early wood density, especially, but also late wood density (Zhang et al 1996, Borders et al 2004).…”

“…For example, in Scots pine (Pinus sylvestris L.) and loblolly pine (Pinus taeda) little or no changes in wood density were observed despite a significant increase in radial growth due to thinning (Tasissa andBurkhart 1997, Mörling 2000). However, in both Norway spruce (Picea abies) and jack pine (Pinus banksiana) a slight decrease in wood density was observed after a thinning, mostly in the lower half of the stem (Petty et al 1990, Barbour et al 1994, Herman et al 1998, Pape 1999a,b, Jaakkola et al 2005.…”

Nonlinear mixed model approaches to estimating merchantable bole volume for Pinus occidentalis

“…The second approach introduces an assumed correlation structure into a generalized least squares solution (Tasissa & Burkhart 1998).…”