Effects of physicochemical characteristics on natural durability of eucalypts woods to wood-decaying fungi

Abstract

This study aimed to relate the biological resistance of seven eucalypt woods to wood-decaying fungi with physicochemical characteristics of wood. Two 12-year-old trees per species were randomly sampled, removing disks at 0 (base), diameter to breast height - DBH, 25, 50, 75, and 100% of the commercial height to determine the wood specific gravity. One basal log of 2.20 m of each wooden species was obtained for chemical analysis and biological tests with brown and white rot fungi (Gleophyllum trabeum, Rhodonia placenta, and Trametes versicolor). For these tests, wood samples were taken in two positions in the radial direction of the trunk in the pith-bark direction (median heartwood and transition region; containing heartwood and sapwood), and the relation between wood natural resistance and physicochemical characteristics was established. Wood specific gravity ranged of 0.51 g cm−3 to 0.73 g cm−3, total lignin of 27.34–32.18%, and holocellulose of 53.39–66.18, not being influenced by pith-bark direction. The extractive and ash contents were affected by the pith-bark direction, in which, in general, the transition region exhibited the highest values contents. The extractive showed a negative relation (−0.67) regarding the loss of mass caused by the fungus Rhodonia placenta. For the holocellulose content, it showed positive relations (0.61; 0.54) to the degradation by Rhodonia placenta and Gleophyllum trabeum, respectively. Independently of the analyzed wood and tested fungus, the median heartwood region was more resistant to wood decay fungi than the transition region.