Calibrating NIR spectroscopy for extractive content of E. bosistoana stem cores
By Yanjie Li and Clemens Altaner, November 2016.
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A meaningful selection/breeding programme requires the assessment of many (i.e. thousands) of individuals. The time and labour requirements of standard durability tests based on fungal decay prohibit their use in a lean breeding programme. As the heartwood extractives are inferring natural durability, the extractive content offers a proxy measurement for natural durability. Heartwood with higher extractive content is likely to be more durable than heartwood with lower extractive content.
The chemical composition of a material (i.e. wood) can be assessed with infrared spectroscopy. Near Infrared (NIR) spectroscopy is used in the agricultural sector to determine product quality i.e. composition. NIR spectroscopy has the advantage of quick measurements (seconds) and little demands on sample preparation, i.e. it is possible to obtain spectra from solid samples. However, NIR spectroscopy is characterised by limited signal resolution (as it assesses vibrational overtones) and a strong influence of moisture. Furthermore it has been reported that the grain angle of solid wood is affecting NIR spectra (e.g. Schimleck et al. 2003).
The extractives content of heartwood of E. bosistoana can be assessed independently of grain angle by NIR spectroscopy. This assists the use of NIR spectroscopy to screen E. bosistoana for heartwood quality.
NIR spectroscopy is not able to predict grain deviations on cores with accuracy suitable for screening purposes.
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