Identification of yellow stringybark (Eucalyptus muelleriana) and silvertop ash (E. sieberi) wood is improved by canonical variate analysis of ray anatomy

Abstract

The woods of yellow stringybark (Eucalyptus muelleriana) and silvertop ash (E. sieberi) are both used for the manufacture of flooring, but yellow stringybark is the preferred species because it contains fewer natural defects and dries faster and with less degrade than silvertop ash. Sometimes companies manufacturing flooring from yellow stringybark find that the wood they process contains higher levels of natural defects than expected, possibly due to the presence of silvertop ash in the wood that they receive from sawmills. It is difficult to prove this, however, because timber from both species looks similar in the rough-sawn condition and is similar anatomically. Hence, a reliable method of identifying the two species is needed. This study used canonical variate analysis to analyse linear combinations of quantitative indicators of ray anatomy in an attempt to clearly separate the wood of the two species. Canonical variate analysis scores derived from the analysis of ray height and cell number, frequency of biseriate rays and frequency of rays per square millimetre were able to completely separate 13 authentic samples of each species. This approach to separating the two species was validated using a further 16 reference specimens provided by industry (eight of each species) and 16 unknown specimens. Analysis of the reference specimens identified one specimen labelled silvertop ash that was clearly yellow stringybark, and one sample of yellow stringybark was identified as silvertop ash. Overall, however, canonical variate analysis of linear combinations of ray features produced fewer misclassifications of the two species than the use of ray parameters on their own. Canonical variate analysis shows promise as a means of more clearly separating yellow stringybark from silvertop ash and may also prove useful in separating those eucalypt wood species whose final identification in taxonomic keys depends on their ray anatomy.