Abstract
Within the wood supply chain, the measurement of roundwood plays a key role due to its high economic impact. While wood industry mainly processes the solid wood, the bark mostly remains as an industrial by-product. In Central Europe, it is common that the wood is sold over bark but that the price is calculated on a timber volume under bark. However, logs are often measured as stacks and, thus, the volume includes not only the solid wood content but also the bark portion. Mostly, the deduction factors used to estimate the solid wood content are based on bark thickness. The aim of this study was to compare the estimation of bark volume from scaling formulae with the real bark volume, obtained by xylometric technique. Moreover, the measurements were performed using logs under practice conditions and using discs under laboratory conditions. The mean bark volume was 6.9 dm3 and 26.4 cm3 for the Norway spruce logs and the Scots pine discs respectively. Whereas the results showed good performances regarding the root mean square error, the coefficient of determination (R2) and the mean absolute error for the volume estimation of the total volume of discs and logs (over bark), the performances were much lower for the bark volume estimations only.
Highlights
Within the wood supply chain, the measurement of roundwood plays a key role due to its high economic impact
The extraction of valuable compounds offers interesting uses for bark, but its potential for new valueadded products is not yet fully e xploited[27,28]. This is why, the interest in bark factors, which allow to estimate the proportion of bark of logs increased[29]. Such equations or models are based on bark thickness measurements
Even if the choice of equation used in determining volume of bark is a source of e rror[20], bark factors with a focus on bark thickness are well studied and the performances of several equations for different tree species show good results[10,11,16,30,33]
Summary
Within the wood supply chain, the measurement of roundwood plays a key role due to its high economic impact. Most of the research on bark proportions is focussed on the bark thickness because bark factors and bark functions are used to predict the diameter under bark (du.b.) from the diameter over bark ( do.b.), in order to estimate the merchantable timber volume under bark ( Vu.b.). To establish such bark functions, bark thickness is measured either using a bark g auge[8,9,10] or by the difference of measurements between d o.b. and d u.b.11–13. To the best of our knowledge, no scientific study analysed the accuracy of those formulae to estimate bark volume using water displacement methods
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