Regional variation in wood modulus of elasticity (stiffness) and modulus of rupture (strength) of planted loblolly pine in the United States

Abstract

Modulus of elasticity (MOE), modulus of rupture (MOR), and specific gravity (SG) are important properties for determining the end-use and value of a piece of lumber. This study addressed the variation in MOE, MOR, and SG with physiographic region, tree height, and wood type. Properties were measured from two static bending samples (dimensions 25.4 mm × 25.4 mm × 406.4 mm) representing each wood type (corewood and outerwood) at heights 2.4, 7.3, and 12.2 m from three trees sampled from 135 loblolly pine (Pinus taeda L.) stands distributed across the natural range of the species. An analysis of variance was conducted to detect the effect of physiographpic region, height, and wood type on each property. Significant regional variation was observed for MOE, MOR, and SG for both wood types with high values in the Gulf and South Atlantic Coastal Plains compared with other regions. A significant height-related trend in MOE, MOR, and SG within a tree was identified; MOE and MOR increased in corewood and decreased in outerwood with height. Maps showing regional variation in MOE and MOR at different heights by wood type were produced and showed significant variation for both properties.Résumé : Le module d'élasticité (MOE), le module de rupture (MOR) et le poids spécifique (PS) sont des propriétés importantes pour déterminer l'usage final et la valeur d'une pièce de bois. Cette étude a porté sur la variation de ces propriétés en fonction de la région physiographique, de la hauteur de l'arbre et du type de bois. Les propriétés ont été mesurées en flexion statique sur deux éprouvettes (dimensions de 25,4 mm × 25,4 mm × 406,4 mm) représentant chaque type de bois (bois juvénile et bois mature) à des hauteurs de 2,4, 7,3 et 12,2 m dans trois arbres prélevés au sein de 135 peuplements de pin à encens (Pinus taeda L.) distribués dans l'ensemble de l'aire de répartition naturelle de l'espèce. Une analyse de variance a été réalisée afin de détecter les effets de la région physiographique, de la hauteur et du type de bois sur chaque propriété. Une variation régionale significative du MOE, du MOR et du PS a été observée dans les deux types de bois, avec des valeurs élevées dans le Golfe et dans les plaines côtières de l'Atlantique Sud comparativement aux autres régions. À l'intérieur de l'arbre, une tendance significative reliée à la hauteur a été identifiée pour le MOE, le MOR et le PS; le MOE et le MOR augmentaient dans le bois juvénile et diminuaient dans le bois mature en fonction de la hauteur. La cartographie des variations régionales du MOE et du MOR à différentes hauteurs et par type de bois montrent que ces deux propriétés varient grandement. [Traduit par la Rédaction]

Wood and Fiber Quality of Plantation-Grown Conifers: A Summary of Research with an Emphasis on Loblolly and Radiata Pine

“…Based on these data, an increasing trend was observed for ring-SG variance from pith to bark, with an overall observed variance of 0.0041 (minimum = 0.0016, maximum = 0.0065, note SG is unitless). Similar variability patterns were also observed in loblolly pine for other wood properties, such as MOE and MOR [37], MFA which decreases with cambial age [38], and wood anatomical characteristics. There is also a trend of increasing wood density with ring number from the pith in radiata pine.…”

“…Over and above the natural variation, silvicultural practices (such as early competition control, pruning, thinning, and fertilization) impart significant change on variation in wood properties within trees. MOE and MOR [37], MFA which decreases with cambial age [38], and wood anatomical characteristics. There is also a trend of increasing wood density with ring number from the pith in radiata pine.…”

“…Models explaining height variation in SG were also developed, based on data from discs collected at various heights of trees, sampled from conventionally managed loblolly pine plantations [112][113][114]. Other than prediction of SG, models to predict radial and longitudinal variation in MFA [38,112,115,116], MOE, and MOR were developed for loblolly pine [37,55]. A schematic representation of predicted within-tree variation in SG and MFA, with ring number from pith, is presented in Figure 3.…”

Bending strength and stiffness of loblolly pine lumber from intensively managed stands located on the Georgia Lower Coastal Plain

“…Jordan et al (2008) found significant differences in the specific gravity of loblolly pine grown across geographic regions with wood grown in the South Atlantic and Gulf regions having the greatest specific gravity while wood in the Hilly Coastal and Piedmont regions having the lowest specific gravity. Antony et al (2011) found similar trends with stiffness and strength of short clear wood specimens. The regional differences are likely linked to the length of juvenile wood production which increases as planting moves north and west from the South Atlantic region; the prevalence of summer moisture in the South Atlantic region allows for greater production of latewood .…”

Comparison of Methods for Estimating Mechanical Properties of Wood by NIR Spectroscopy

“…However, NIR technology can complement the standard methods, for example, to measure applied loads [15], or in applications where the accuracy of a single value is not critical. Examples include studies of within-tree variation in MOE [29] or regional variation in MOE and MOR [30]. In such studies, the use of NIR-estimated values can greatly improve approximations of how properties vary spatially.…”