The term extractives defines chemical compounds of different classes that can be extracted from wood or bark by means of polar or non-polar solvents. Extractives are derived mostly from the metabolic processes of the tree, particularly the sapwood to heartwood transformation. The first objective of the research was to study the distribution of extractives within Sitka spruce trees at different heights in the trunk, as well as the distribution between bark, rootwood, knotwood, heartwood and sapwood. The second aim of the work was to learn about the influence of yield class, site elevation, North/East location and thinning on the extractives content and composition of Sitka spruce across Scotland.The samples were sawdust obtained in different ways from either discs, knots or roots sawn from Sitka spruce trees freshly cut in the forest, or collected during the coring of trees from 64 sites all around Scotland and northern England.The extraction was carried out on Soxhlet extractors using acetone as solvent. Two analytical techniques were used: gas chromatography and Fourier transform infrared spectroscopy.The results of the research showed that the extractive content and composition of Sitka spruce differed according to the type of wood studied with the largest amount detected in bark and the lowest in heartwood and sapwood. The last two types of wood were studied in more detail, showing that the difference in extractive content between heartwood and sapwood was consistent at all heights in the trunk.The chromatographic analysis of heartwood, sapwood, knotwood, rootwood and bark showed that their compositions differed slightly from published data on Norway spruce.
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