Application of near infrared spectroscopy to a diverse range of species demonstrating wide density and stiffness variation

The application of near infrared (NIR) spectroscopy to a large number of mixed species that display extremely wide variations in wood chemistry, anatomy and physical properties, is described. The mixed species samples were characterized in terms of density, longitudinal modulus of elasticity and microfibril angle. NIR spectra were obtained from the radial/longitudinal face of each sample and used to generate calibrations for the measured physical properties. The calibrations developed for density and longitudinal modulus of elasticity bad the highest coefficients of determination (R-2) and demonstrated that it is possible to develop general calibrations for these important wood properties across a wide range of species. The mixed species calibrations were used to estimate wood properties of two species, Eucalyptus delegatensis R.T. Baker and Pinus radiata D. Don. The results obtained for density and longitudinal modulus of elasticity indicated that mixed species calibrations can be used to rank trees, In practice the extreme variation of samples selected for this study would not be required. It is expected that refinement of calibrations, through sample selection, would provide more accurate prediction of physical properties.