High resolution scanning of radial strips cut from increment cores by near infrared spectroscopy

Abstract

Near infrared (NIR) spectroscopy provides a rapid method for the determination of wood properties of radial strips. The spatial resolution of the NIR measurements has generally been limited to sections 10 mm wide and as a consequence the estimation of wood properties of individual rings or within rings has not been possible. Many different NIR instruments can be used to collect NIR spectra from the surface of radial strips at relatively high spatial resolution and the purpose of this study was to compare wood property calibrations obtained using NIR spectra collected in 5 mm and 2 mm sections with several different NIR instruments. We found that calibrations based on spectra collected in 5 mm sections had good statistics, with those based on the Bruker Vector 22/N spectrometer the strongest. Of the three properties examined (density, microfibril angle and stiffness), density had the weakest statistics. When the spatial resolution was decreased to 2 mm, calibration and prediction statistics were weaker than those at 5 mm. RPDp's were relatively low with the highest being 1.76 for predicted stiffness based on NIR spectra obtained using the ASD Field Spec Pro spectrometer. Based on the low RPD p's, we conclude that none of the instruments examined were suitable for scanning radial strips at a spatial resolution of 2 mm.