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 total of 30 Caesalpinia echinata (pernambuco) sticks were ranked based on their suitability for making high quality bows and were assigned to one of the three following categories: 0=very poor to poor, 1=good to very good, and 2=excellent. From the end of each stick a sample was cut for wood property and near infrared (NIR) spectroscopic analysis. Wood properties measured included air-dry density, extractives content, microfibril angle, stiffness and wood color. NIR spectra were evaluated by principal component analysis (PCA) and on the PC scores. Poor quality samples were discriminated from those of good to very good and excellent quality; however, samples from the two higher quality groups were mixed. Based on relationships observed between PC scores and wood properties, we suggest that, of the measured properties, density and stiffness were the most important in sample discrimination based on quality. Samples ranked in the excellent category had high average density (1119 kg m-3) and stiffness (25.2 GPa) and relatively low extractives content (21.2%) compared to samples in the very poor to poor category (density= 938 kg m-3, stiffness=18.9 GPa and extractives content=24.9%).
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