1. E-mail: yanjie.li@pg.canterbury.ac.nz
Predicting extractive content of Eucalyptus bosistoana heartwood by near infrared spectroscopy
Yanjie Li and Clemens Altaner School of Forestry, University of Canterbury, Christchurch, New Zealand
Background
Eucalyptus bosistoana produces class 1 naturally durable heartwood, has a fast growth and grows in New Zealand conditions. NZDFI has established a large scale breeding programme to improve wood properties of the species, including natural durability. Traditional methods to determine natural durability are time and cost consuming. The extractive content (EC) is the most important factor providing natural durability. Near infrared spectroscopy (NIR) is a quick and cheap non-destructive technique used for the chemical analysis of agricultural products. It has been used to determine the quantity of heartwood extractives in some tree species. This project evaluates the use of NIR to predict the extractive content in E. bosistoana by NIR with the aim to be used in a breeding programme.
NIR calibration
Discs from 53 trees where collected and dried. NIR spectra were taken from the isolated heartwood. The heartwood was milled and extracted with ethanol. A PLSR (partial least squares regression) algorithm was used to develop a prediction model for the amount of ethanol extract in wood from the NIR spectra. Figure 1 shows the accuracy of the prediction model, which was comparable to what was reported for other species (Taylor et al. 2011).
CONCLUSION: NIR can be used to accurately predict EC in E. bosistoana.
Figure 1: Measured vs predicted EC (%) in E. bosistoana
Extractive distribution in E. bosistoana
NIR analysis revealed that the extractive content of E. bosistoana heartwood decreased towards the pith (Figure 2). This is not obvious form the appearance of the wood (Figure 3). Such radial profiles in extractive content have been reported for other species (Sherrard and Kurth 1933).
CONCLUSION: When assessing heartwood quality of E. bosistoana trees the radial EC distribution needs to be considered.
EC (%)
Figure 2: EC predicted by NIR in a 40 year old E. bosistoana tree at the stem base
Figure 2: Heartwood and sapwood in a 40 year old E. bosistoana tree at the stem base
Acknowledgements
This work was funded by Future Forests Research (FFR) Specialty Wood Products Partnership
References
Taylor et al. (2011) NIR-based prediction of extractives in American white oak heartwood. Holzforschung 65:
Sherrard and Kurth (1933) Distribution of extractive in redwood - Its relation to durability. Industrial and Engineering Chemistry 25: