Resistência natural da madeira de sete espécies de Eucalyptus a agentes xilófagos
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Data
2017-02-17
Autores
Medeiros Neto, Pedro Nicó de
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Universidade Federal do Espírito Santo
Resumo
This study aimed to evaluate the natural wood resistance of seven Eucalyptus wood species in laboratory and field xylophagous tests and to correlate their durability with physical-chemical and anatomical characteristics. Two trees with 12 years old were randomly sampled by species and from each set of discs at 0, DBH, 25, 50, 75 and 100% of the commercial height, to determine anatomical characteristics and specific gravity. One log of 2.20m obtained from the first section of each tree were used to the chemical analysis and biological tests. For these tests, samples were taken in two positions in the radial direction of the trunk in the pith-bark direction (intermediate heartwood and transition region; containing heartwood and sapwood) and relationship were made among natural resistance and physical-chemical and anatomical characteristics. In the analysis and evaluation of the tests, the Scott - Knott test (p = 0.05) was used. The relationships among the variables studied were evaluated through simple linear regression. The Corymbia citriodora wood exhibited the largest specific gravity and Eucalyptus grandis the smaller. The E. camaldulensis wood had a higher extractive content and lower holocellulose content and C. citriodora wood had higher ash content. E. camaldulensis presented the lowest value of holocellulose. For the other species, holocellulose and lignin contents were close, and similar in the positions evaluated. In choice feeding tests, the E. robusta, E. grandis and E. uroplylla wood were the most consumed by termites, and C. citriodora wood was the least susceptible to attack by dry wood termite and no-choice feeding tests. The fungus Trametes versicolor degraded less the wood from the intermediate heartwood. To Postia placenta and Gloeophyllum trabeum fungi, in most species the intermediate heartwood was less resistant. The intermediate heartwood exhibiting minor color variation for all species attacked by Trametes versicolor and for the Postia placenta and Gloeophyllum trabeum the region transition was more vulnerable to color change. For the soil bed and field decay tests, the transition region exhibited the greatest mass losses. Regarding the relationships, the chemical characteristics were more relevant to the tests with termites, mainly to the dry wood termite. The anatomical variables were better correlated with the fungal attack on the wood. Overall, when evaluating the natural resistence indexes of woods to xylophagous fungal attack, the species with more durability were E. camaldulensis and C. citriodora and E. grandis the less resistent.
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Biological assay , Wood characteristics , Colorimetry , Linear correlation , Ensaios biológicos , Características da madeira , Correlação linear