Estimation of microfibril angle of increment cores by near infrared spectroscopy

Abstract

Eight Pinus radiata D. Don (Radiata pine) increment core samples representative of a total of thirty-two increment cores were selected. NIR spectra were obtained from the radial-longitudinal face of each core in 10-mm increments and used to develop a microfibril angle (MFA) calibration. The MFA calibration was developed using seven factors giving an excellent relationship between SilviScan-2 determined MFA and NIR fitted MFA (coefficient of determination (R2) = 0.95) and a standard error of calibration (SEC) of 1.8 degrees. The MFA calibration was used to predict the MFA of NIR spectra obtained in 10-mm sections from the radial-longitudinal face of two intact P. radiata increment cores. NIR predicted MFA was found to be in excellent agreement with MFA determined by SilviScan-2, with R2 of 0.98 (core A) and 0.96 (core B). The standard error of prediction (SEP) for core A (1.0 degree) was much lower than for core B (2.5 degrees). Both sets of predictions closely followed the patterns of MFA radial variation determined by SilviScan-2. NIR spectroscopy provides a rapid method for determining MFA variation in increment cores and is suitable for the routine analysis of large numbers of samples.