CHANGES IN SHRINKAGE AND COLLAPSE IN THE WOOD OF EUCALYPTUS-REGNANS F MUELL FOLLOWING EXTRACTION

An examination of shrinkage and collapse in solid wood Segments of Eucalyptus regnans following sequential extraction by hot water, hot methanol and hot NaOH has demonstrated complex changes in these properties with respect to radial distribution in the tree. In the heartwood, the slope of regression lines relating collapse to distance from the periphery underwent successive reversals from positive (unextracted) to negative (hot water extracted) to positive (methanol extracted) to negative (NaOH extracted). Nevertheless, after adjustments the difference between collapse following extraction and collapse before extraction was shown to be negatively related to the percentage of extractives removed at all stages. Similar differences in shrinkage after reconditioning were positively related to the percentage of extractives removed except after NaOH extraction. Collapse increased after hot water extraction but decreased after cold water extraction. However, changes in radial distribution after cold water were similar to those observed after hot water extraction. In the sapwood there tended to be little change in shrinkage and collapse after hot water, cold water or methanol extraction. After NaOH extraction, substantial increases were recorded, but these were less than half those observed for heartwood. The possible influence on collapse by heat effects during extraction is discussed. Extraction with hot and cold water increased the significance of the relationship between shrinkage after reconditioning and basic density thereby demonstrating greater compliance with the Stamm formula (S = fϱ). These effects were most pronounced in the heartwood. © 1990 Walter de Gruyter