Prediction of loblolly pine wood properties using transmittance near-infrared spectroscopy

Near-infrared (NIR) spectroscopy is a rapid nondestructive technique that has been used to characterize chemical and physical properties of a wide range of materials. In this study, transmittance NIR spectra from thin wood wafers cut from increment cores were used to develop calibration models for the estimation of α-cellulose content, av- erage fiber length, fiber coarseness, and lignin content in the laboratory. Eleven-year-old trees from two sites were sam- pled using 12-mm increment cores. Earlywood and latewood of ring 3 and ring 8 from these samples were analyzed in the laboratory using microanalytical methods for α-cellulose content, average fiber length, fiber coarseness, and lignin content. NIR calibrations and laboratory measurements based on one site were generally reliable, with coefficients of determination (R 2 ) ranging from 0.54 to 0.88 for average fiber length and α-cellulose content, respectively. Predicting ring 8 properties using ring 3 calibration equations showed potential for predicting α-cellulose content and fiber coarse- ness, with R 2 values of approximately 0.60, indicating the potential for early selection. Predicting the wood properties using the calibration equations from one site to predict another showed moderate success for α-cellulose content (R 2 = 0.64) and fiber coarseness (R 2 = 0.63), but predictions for fiber length were relatively poor (R 2 = 0.43). Prediction of lignin content using transmittance NIR spectroscopy was not as reliable in this study, partially because of low variation in lignin content in these wood samples and large errors in measuring lignin content in the laboratory. Resume : La spectroscopie dans le proche infrarouge (PIR) est une methode rapide et non destructive qui a ete utilisee pour caracteriser les proprietes chimiques et physiques d'une vaste gamme de materiaux. Dans cette etude, les spectres de transmittance PIR de minces copeaux de bois preleves sur des carottes ont ete utilises pour developper des modeles capables d'estimer le contenu en α-cellulose, la longueur moyenne des fibres, la grosseur du grain et le contenu en li- gnine mesures en laboratoire. Des arbres âges de 11 ans ont ete echantillonnes dans deux stations en prelevant des ca- rottes de 12 mm. Le bois initial et le bois final des cernes trois et huit de ces echantillons ont ete analyses en laboratoire a l'aide de techniques micro-analytiques pour determiner le contenu en α-cellulose, la longueur moyenne des fibres, la grosseur du grain et la lignine. L'etalonnage PIR avec les mesures en laboratoire basees sur les echantil- lons d'une station etait generalement fiable avec des coefficients de determination (R 2 ) variant respectivement de 0,54 a