Estimation of wood stiffness of increment cores by near infrared spectroscopy: The development and application of calibrations based on selected cores

Eight Pinus radiata D. Don (Radiata pine) increment core samples representative of a total of thirty-two increment cores were selected for the development of an E-L(SS) (longitudinal modulus of elasticity calculated from SilviScan-2 data) calibration based on NIR spectra obtained from the radial-longitudinal face of each sample in 10-mm increments. The primary aim of the work was to investigate if an E-L(SS) calibration developed using a subsample of cores representative of a larger set provided better predictions of E-L(SS) than those reported in Schimleck et al. (2002a). The E-L(SS) calibration was developed using eight factors giving an excellent relationship between SilviScan-2 determined E-L(SS) and NIR fitted E-L(SS) (coefficient of determination (R-2) = 0.97) and a low standard error of calibration (SEC) (0.91 GPa). To test the E-L(SS) calibration, NIR spectra were obtained in 10-mm sections from the radial-longitudinal face of two intact R radiata increment cores and E-L(SS) of each section predicted. NIR estimates of E-L(SS) were in excellent agreement with E-L(SS) determined using SilviScan-2 data, with R-2 of 0.99 (core A) and 0.98 (core B). Standard error of predictions (SEP) of 1.6 GPa (core A) and 1.2 GPa (core B) were obtained. Both sets of predictions closely followed the patterns of E-L(ss) radial variation determined experimentally. E-L(SS) calibration based on NIR spectra obtained from a set of representative cores can provide excellent predictions of E-L(SS). The predictions were superior to those reported in Schimleck et al. (2002a).