Near infrared spectroscopy for the nondestructive estimation of clear wood properties of Pinus taeda L. from the southern United States

The estimation of specific gravity (SG), modulus of elasticity (MOR), and modulus Of rupture (MOR) of loblolly pine (Pinus taeda L.) clear wood samples from a diverse range of sites across the southern United States was investigated using near infrared (NIR) spectroscopy. NIR spectra were obtained from the radial and cross sectional (original, rough,and sanded) surfaces of blocks cut from the ends of 280 clear wood samples (140 matching juvenile and mature wood). Calibrations based only on juvenile Or mature wood samples had weak calibration statistics and failed to perform well when applied to a separate test set. Calibrations developed using both juvenile and mature wood NIR spectra provided good relationships for all properties with coefficients of determination (r(2)) ranging from 0.82 (MOE, radial face)to 0.90 (SG, radial face)demonstrating that it is possible to obtain Multi-Site calibrations for SG, MOE, and MOR estimation. Prediction r(2) ranged from 0.77 (MOE, radial face and SG, original cross-sectional face) to 0.86 (MOR, sanded cross-sectional face). Though differences between surfaces were small, on average the sanded cross-sectional surface provided the best calibration and prediction statistics.