Natural Durability of the Heartwood of Coast Redwood [Sequoia Sempervirens (D.Don) Endl.] and its Prediction Using near Infrared Spectroscopy

Abstract

The heartwood of plantation-grown coast redwood trees from three forests in the North Island, New Zealand, was evaluated using in vitro decay tests with fungal cultures to determine variation in natural durability and its prediction using near infrared (NIR) spectroscopy. The NIR spectra were acquired from the solid wood surface, prior to decay testing, using a fibre-optic probe attached to a Bruker MPA FT-NIR spectrometer and an imaging spectrograph coupled to a NIR line camera. The partial least squares (PLS) regression models of mass loss with fungal decay testing, based on spectra collected with the FT-NIR spectrometer, had better predictive performance than the NIR line camera, as evidenced by fewer latent variables and slightly better R2. The ratios of prediction to deviation ( RPD) were 1.3 to 1.4 for both the spectrometer and camera system, which suggests the PLS regression models could be used to segregate the heartwood of coast redwood for high- and low values of natural durability.