Rapid analysis of the microfibril angle of loblolly pine from two test sites using near-infrared analysis

Abstract

There have been several recent studies employing near infrared (NIR) spectroscopy for the rapid determination of microfibril angle (MFA). However, only a few have utilized samples cut from individual rings of increment cores, and none have been as large as this present study, sampling over 600 trees from two test sites producing over 3000 individual ring samples for MFA analysis. This has allowed the use of individual growth ring models rather than using those based on earlywood, latewood, corewood or outerwood. It was observed that for both test sites, the strongest models were from the “All”, earlywood and latewood sample sets. The individual growth ring calibration models provided poorer RPD values despite using over 200 samples in the analyses. In general, the results from the test samples largely mirrored those from the corresponding calibration samples. Corresponding test sample predictions from the opposing site were noticeably poorer than test samples from the same site. Thus, a greater variation in the number of sites would provide improved model robustness. This study has found that the models based on individual ring samples were not as strong as those obtained in other studies based on the radial-longitudinal face of wood strips, spread over several growth rings.