Estimation of wood stiffness of increment cores by near-infrared spectroscopy

The use of calibrated near-infrared (NIR) spectroscopy for predicting the radial variation of the longitudinal modulus of elasticity (E-L) of increment cores is described. Sets of Eucalyptus delegatensis R.T. Baker (alpine ash) and Pinus radiata D. Don (radiata pine) samples were characterized in terms of E-L(SS) (estimated stiffness based on a combination of SilviScan-2 diffractometric data and measured density (R. Evans and J. Ilic. 2001. For. Prod. J. 51(3): 53-57)). NIR spectra, obtained from the radial-longitudinal face of each sample, were used to develop E-L(SS) calibrations for the E. delegatensis and P. radiata sample sets and the two sets combined. The relationships between laboratory-determined E-L(SS) and NIR-fitted E-L(SS) were good in all cases. E-L(SS) was estimated in separate test sets and found to correlate well with measured E-L. NIR spectra were obtained in 15-mm sections from the radial-longitudinal face of two intact P. radiata increment cores. E-L(SS) of each section was estimated using the P. radiata and the combined P. radiata and E. delegatensis calibrations. NIR estimates of E-L(SS) were in good agreement with SilviScan-2 determined stiffness indicating that NIR spectroscopy can be successfully used to estimate radial variation in wood stiffness of increment cores.