Response of near Infrared Diffuse Reflectance Spectra to Blue Stain and Wood Age

We analysed 320 increment cores at 10 different growth ring positions for a net total of 2691 ring samples, all taken from breast height. The objective of this research was to (a) detect which wavelengths were sensitive to blue stain and (b) determine which wavelengths were sensitive to age when subjected to chemometric interpretation. It was found that wood chemistry-associated wavelengths 1115–1195 nm were most sensitive to blue stain while those at 1335–1415 nm and 1655–1685 nm were also influenced by blue stain, but to a lesser extent. When blue stained samples are not included in the calibration set, but blue stain then occurs in the field, bias in lignin prediction may be more likely, since wavelengths associated with lignin were more sensitive to blue stain. Alternatively, lignin-associated wavelengths showed clear delineation in absorbance with age while the relationship between cellulose-associated wavelengths and age was apparent, but less clear.