Differentiation of some Canadian coniferous woods by combined diffuse and specular reflectance Fourier transform infrared spectrometry
Creators: name: Nault, Jason Ray
Publisher: name: University of British Columbia
Year: 2011

description: A new method is presented for rapid differentiation between coniferous woods commonly found in mixtures in major lumber producing regions of British Columbia. The species mixtures differentiated are the group known as "spruce/ pine/ fir" (SPF) containing white spruce (Picea glauca Voss), lodgepole pine (Pinus contorta Dougl.) and subalpine fir (Abies lasiocarpa Nutt.); the pair western larch (Larix occidentalis Nutt.) and Douglas-fir (Pseudotsuga menziesii Franco.); and the group of western hemlock (Tsuga heterophylla Sarg.), Sitka spruce (Picea sitchensis Carr.) and amabilis fir (Abies amabilis Dougl.). The method entailed measuring the reflectance infrared spectrum of a sample set of small wood pieces at a resolution of two wave numbers, determining which wavelengths were useful for differentiating species through a combination of correlation analyses and principal component analyses and using measurements at these wavelengths to develop species models using discriminant analysis. These models were then used to classify a larger set of samples measured under the same conditions. This approach was used to classify both green wood samples and the same samples after freeze-drying. For the SPF group the most effective overall classification model for the dry samples used 30 wavelengths and correctly classified 76% of samples, including 74% of heartwood samples and 89% of sapwood samples. For the green samples, the most effective sort used 10 wavelengths and correctly assigned species to 83% of green samples representing 84% of heartwood samples and 76% of sapwood samples. Classification was unsuccessful when the same classification parameters were applied to a matched set of extractive-free SPF samples, indicating that the sorting criteria are dependant upon the presence of extractive chemicals, both in heartwood and sapwood. The same classification parameters applied to a SPF mixture from eastern Canada (black spruce (Picea mariana B.S.P.), white spruce (Picea qlauca Voss.), jack pine (Pinus banksiana Lamb.), red pine (Pinus resinosa Ait.), white pine (Pinus strobus L.) and balsam fir (Abies balsamea Hill) were less successful than for the western SPF mixture. This suggests that each species may have unique sorting criteria based upon the somewhat different extractive chemical complex present in its wood. For the western larch/ Douglas-fir, the most effective overall classification model used 18 wavelengths and classified 98% of dry samples correctly for both heartwood and sapwood. For green samples, the best sort used 12 wavelengths and correctly assigned species to 91% of green samples, representing 90% of heartwood samples and 91% of sapwood samples. For the western hemlock/ Sitka spruce/ amabilis fir mixture, the most effective sort for the dry samples correctly classified 83% of the samples, 85% of heartwood samples and 56% of sapwood samples. Classification of the green samples proved difficult, with the best sort only 67% correct and using 15 wavelengths. However, if only western hemlock and Sitka spruce were sorted, the effectiveness rose to 82%.