Abstract
Applicability of near infrared (NIR) spectroscopy to identify species of degraded and aging solid wood was examined among species important to Japanese art history and archaeology. NIR spectra were obtained from wood blocks of five softwood species collected over the last 80 years from various sites and stored in the wood library of the Forestry and Forest Products Research Institute, Tsukuba in Japan. Partial least square (PLS) discriminant analysis was employed for the separation of three pairs of species, i.e., Chamaecyparis obtusa and Torreya nucifera, Chamaecyparis obtusa and Chamaecyparis pisifera, Thuja standishii and Cryptomeria japonica. The effects of spectral pre-processing and wavelength range were also evaluated. Under the limitation of sample volume, PLS discriminant analysis calibrated using second derivatives and wavelengths spanning 830 to 1150 nm could separate the samples into each pair of species in the 100 % accuracy. These results suggest that NIR spectroscopy combined with PLS discriminant analysis is a powerful technique for distinguishing species for degraded and aging wood nondestructively without any sample preparations.
