Five families of competition indices were evaluated and compared on the basis of simple correlation with loblolly pine individual tree growth and multiple correlation with growth in the presence of other tree and stand attributes. The family of distance-independent indices included various relative size measures in the form of tree size to mean size ratios. Crown ratio was also included as a distance-independent measure. The four families of distance-dependent indices included various influence area overlap indices, distance-weighted size ratio indices, Spurr's point density, and Brown's point density or area potentially available (APA). All indices were significantly correlated with dbh and basal area growth. The relative size ratio indices, crown ratio, Spurr's point density, and several APA variations were judged best in simple correlations after accounting for tree size and stand density. The best distance-dependent indices had little if any advantage, either in simple or multiple correlation, over the best distance-independent indices. However, the point density index of Spurr and especially APA contributed significantly to growth prediction even in the presence of tree size, stand density, and the distance-independent size ratio and crown ratio indices. Further, APA had the highest partial correlation when all variables were included in this multiple correlation. It was concluded the APA would be a good index for growth prediction models when other tree and stand attributes are already known.

Preliminary studies based on small sample sets show that near infrared (NIR) spectroscopy has the potential for rapidly estimating many important wood properties. However, if NIR is to be used operationally, then calibrations using several hundred samples from a wide variety of growing conditions need to be developed and their performance tested on samples from new populations. In this study, 120 Pinus taeda L. (loblolly pine) radial strips (cut from increment cores) representing 15 different sites from three physiographic regions in Georgia (USA) were characterized in terms of air-dry density, microfibril angle (MFA), and stiffness. NIR spectra were collected in 10-mm increments from the radial longitudinal surface of each strip and split into calibration (nine sites, 729 spectra) and prediction sets (six sites, 225 spectra). Calibrations were developed using untreated and mathematically treated (first and second derivative and multiplicative scatter correction) spectra. Strong correlations were obtained for all properties, the strongest R2 values being 0.83 (density), 0.90 (MFA), and 0.93 (stiffness). When applied to the test set, good relationships were obtained (Rp2 ranged from 0.80 to 0.90), but the accuracy of predictions varied depending on math treatment. The addition of a small number of cores from the prediction set (one core per new site) to the calibration set improved the accuracy of predictions and importantly minimized the differences obtained with the various math treatments. These results suggest that density, MFA, and stiffness can be estimated by NIR with sufficient accuracy to be used in operational settings.

Loblolly pine (Pinus taeda L.) is the most important plantation species in the southeastern United States and specific gravity (SG) is its most important wood quality trait. Analysis of annual ring SG of breast height (1.37 m) increment cores from 3957 trees representing 147 plantations across the species natural range showed that ring SG increases with increasing age and varies significantly among physiographic regions. The South Atlantic and Gulf regions had the highest ring SGs, while the Hilly and Piedmont regions had the lowest. Based on ring SG, the juvenile period averages 4.3 years, followed by 8.6 years of transition wood, with mature wood produced by year 13. Whole-core mean SG was significantly higher in the South Atlantic (0.486) compared with the other regions (mean = 0.455), which were not statistically different from each other. Trees from the South Atlantic have significantly higher whole-core SG because they contain significantly more latewood (40.1%) compared with trees growing in other regions (33.8%). Maps indicate that stands in the South Atlantic and Gulf regions have the highest SG at a given age. Stands growing on the northern and western fringe of the natural range of loblolly pine have the lowest whole-core SG.Résumé : Le pin à encens (Pinus taeda L.) est la plus importante espèce plantée dans le sud-est des É tats-Unis d'Amérique et la densité est la plus importante caractéristique de la qualité du bois chez cette essence. L'analyse de la densité des cernes annuels dans des carottes prélevées à hauteur de poitrine (1,37 m) sur 3957 arbres provenant de 147 plantations établies partout dans l'aire naturelle de répartition de l'espèce montre que la densité des cernes annuels augmente avec l'âge et varie significativement entre les régions physiographiques. Les cernes annuels des régions de l'Atlantique Sud et du Golfe ont les densités les plus élevées tandis que ceux des régions de Hilly et du Piedmont ont les plus faibles. Sur la base de la densité des cernes annuels, la période juvénile dure en moyenne 4,3 ans, suivie d'une période de transition de 8,6 ans et du bois mature vers l'âge de 13 ans. La densité moyenne de l'ensemble de la carotte est significativement plus élevée dans la région de l'Atlantique Sud (0,486) que dans les autres régions (moyenne = 0,455) qui ne sont pas statistiquement différentes les unes des autres. Les carottes des arbres de la région de l'Atlantique Sud ont une densité significativement plus élevée parce qu'ils contiennent significativement plus de bois final (40,1 %) que les arbres qui croissent dans les autres régions (33,8 %). Pour un âge donné, les cartes indiquent que les peuplements des régions de l'Atlantique Sud et du Golfe ont la densité la plus élevée. Les carottes provenant des peuplements qui croissent aux limites nord et ouest de l'aire naturelle de répartition du pin à encens ont les plus faibles densités.[Traduit par la Rédaction]

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The application of near infrared (NIR) spectroscopy to the green wood of radial samples (simulated increment cores) and the development of calibrations for the prediction of wood properties are described. Twenty Pinus taeda L. (loblolly pine) radial strips were characterized in terms of air-dry density, microfibril angle (MFA), and stiffness. NIR spectra were obtained in 10-mm steps from the radial longitudinal and transverse faces of each sample and used to develop calibrations for each property. NIR spectra were collected when the wood was green (moisture content ranged from approximately 100% to 154%) and dried to approximately 7% moisture content. Relationships between measured and NIR estimates for green wood were good; coefficients of determination (R2) ranged from 0.79 (MFA) to 0.85 (air-dry density). Differences between calibrations developed using the radial longitudinal and transverse faces were small. Calibrations were tested on an independent set. Predictive errors were relatively large for some green samples and relationships were moderate; R2p ranged from 0.67 (MFA) to 0.81 (stiffness). Dry wood calibrations demonstrated strong predictive relationships with R2p ranging from 0.87 (air-dry density) to 0.95 (stiffness). NIR spectroscopy has the potential to predict the air-dry density, MFA, and stiffness of 10-mm sections of green P. taeda wood samples.

Acoustic tools are increasingly used to estimate standing-tree (dynamic) stiffness; however, such techniques overestimate static stiffness, the standard measurement for determining modulus of elasticity (MOE) of wood. This study aimed to identify correction methods for standing-tree estimates making dynamic and static stiffness comparable. Sixty Pinus taeda L. trees, ranging from 14 to 19 years old, obtained from genetic tests established in the southeastern United States, were analyzed. Standing-tree acoustic velocities were measured using the TreeSonic tool. Acoustic velocities were also recorded in butt logs cut from the same trees using the Director HM200. A strong but biased relationship between tree and log velocities was observed, with tree velocities 32% higher (on average) than the corresponding log velocities. Two correction methods, one for calibrating tree velocities and one for accounting for differences in wood moisture content, were used to determine an adjusted MOE. After correction, adjusted MOE estimates were in good agreement with static longitudinal MOE values measured on clearwood specimens obtained from the trees, and no systematic bias was observed. The results of this study show that acoustic estimates of MOE on standing trees largely depend on how the data are processed and the reference method used.Résumé : Des outils acoustiques sont de plus en plus utilisés pour estimer la rigidité (dynamique) des arbres debout. Cependant, de telles mesures surestiment la rigidité statique, la technique standard pour déterminer le module d'élasticité (MOE) du bois. Cette étude visait à identifier les méthodes de correction des estimations sur les arbres debout pour rendre les valeurs de rigidité dynamique et statique comparables. Soixante tiges de Pinus taeda L. ont été analysées. Elles étaient âgées de 14 à 19 ans et provenaient de tests génétiques établis dans le sud-est des É tats-Unis. La vitesse sonique dans les arbres debout a été mesurée avec l'appareil TreeSonic. La vitesse sonique a aussi été mesurée dans la bille de pied coupée chez les mêmes arbres avec le Director HM200. Une relation étroite mais biaisée a été observée entre la vitesse sonique dans les arbres debout et les billes. La vitesse sonique était en moyenne 32 % plus élevée dans les arbres que dans les billes. Deux méthodes de correction ont été utilisées pour déterminer un MOE ajusté : une méthode pour calibrer la vitesse sonique dans les arbres et une autre pour tenir compte de la différence d'humidité dans le bois. Après avoir effectué la correction, les estimations du MOE ajusté correspondaient bien aux valeurs du MOE longitudinal statique mesuré sur des échantillons de bois sain provenant des arbres et aucun biais systématique n'a été observé. Les résultats de cette étude montrent que les estimations acoustiques du MOE chez les arbres debout dépendent largement de la façon dont les données sont traitées et de la méthode de référence utilisée.[Traduit par la Rédaction]

A modified logistic function was used for modeling specific-gravity profiles obtained from X-ray densitometry analysis in 675 loblolly pine (Pinus taeda L.) trees in four regeneration trials. Trees were 21 or 22 years old at the time of the study. The function was used for demarcating corewood, transitional, and outerwood zones. Site and silvicultural effects were incorporated into the model. Heteroscedasticity and within-group correlation were accounted for by specifying the variance and serial-correlation structure, respectively. The estimated transition zone was located between rings 5 and 15, and the outerwood demarcation point varied from rings 12 to 15. No effects of treatments on the demarcation points were observed; however, site preparation and fertilization affected the lower asymptotes of the curves in all sites. A geographical trend for the demarcation point was observed, with the northern site requiring more time to reach a plateau in specific gravity compared with the southern sites. The diameter of the juvenile core was increased as a result of the treatments. However, the amount of corewood was not statistically affected, ranging from 55% in the north to 75% in the south, except at one site where fertilization decreased the percentage of corewood.Résumé : Une fonction logistique modifiée a été utilisée pour modéliser les profils de densité obtenus par densitométrie chez 675 pins à encens provenant de quatre essais de régénération. Les arbres avaient 21 ou 22 ans au moment de l'étude. La fonction a été utilisée pour différencier les zones de bois juvénile, de bois de transition et de bois adulte. Les effets de la station et de la sylviculture ont été incorporés dans le modèle. En spécifiant la structure de la variance et de l'autocorrélation, on a respectivement tenu compte de l'hétéroscédasticité et de la corrélation dans les groupes. On a estimé que la zone de transition était située entre les cernes 5 et 15 et que le point de démarcation du bois adulte variait entre les cernes 12 à 15. Les traitements n'ont eu aucun effet sur les points de démarcation. Cependant, la préparation de terrain et la fertilisation on affecté l'asymptote inférieure des courbes dans toutes les stations. Une tendance géographique a été observée au sujet du point de démarcation : la densité prenait plus de temps pour atteindre un plateau dans la station située au nord que dans les stations plus au sud. Les traitements ont augmenté le diamètre du coeur juvénile. Cependant, la quantité de bois juvénile n'a pas été statistiquement affectée, variant de 55 % au nord à 75 % au sud, à l'exception d'une station où la fertilisation a entraîné une diminution du pourcentage de bois juvénile.[Traduit par la Rédaction]

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