NATURAL DURABILITY OF Eucalyptus dunnii Maiden, Eucalyptus robusta Sm., Eucalyptus tereticornis Sm. AND Hovenia dulcis Thunb. WOOD IN FIELD AND FOREST ENVIRONMENT

Abstract

-This study aimed at evaluating the natural durability of Eucalyptus dunnii, Eucalyptus robusta, Eucalyptus tereticornis and Hovenia dulcis woods submitted to a deterioration test in two environments, field and forest. The test samples were buried until half of their length (150 mm). Evaluations were carried out each 45 days, totalizing a 405-day period, with three-repetition withdrawal of each species for environment, totalizing nine samples from each environment, making up 24 test samples for evaluation. After percentage calculations of mass loss and resistance degree classification, the deterioration index was adopted for decomposition evaluation and fungal decay potential determination of test samples. The study has been carried out in completely randomized design (CRD), evaluated through analysis of variance (ANOVA) with subsequent comparison of means by Turkey's test, in a 5%-level of probability of error, along with regression analysis. Eucalyptus tereticornis wood presented lesser mass loss in both environments. Hovenia dulcis presented lesser deterioration probability in both environments. Forest environment test samples presented greater mass loss percentages and lesser deterioration index.

Sixteen properties of Eucalyptus Tereticornis wood for structural uses

“…This research was based on physical and mechanical properties evaluation of Eucalyptus tereticornis species because of lack of information about this timber characterization for construction. In short, this gap has not been filled, because recent studies only have evaluated its timber properties essentially for decay resistance, weather resistance, and/or natural durability such as revealed Carvalho et al (2016), Delucis et al (2016a;2016b), Lazarotto et al (2016). Then, this present research is necessary for better utilization of this species in timber industry.…”

Resistência e rigidez da madeira de espécies florestais submetidas a campo de apodrecimento

“…A suscetibilidade ao ataque de fungos de podridão parda e podridão branca para as mesmas espécies foi analisado por Carvalho et al (2015) onde os autores indicam o E. robusta como espécie menos propensa ao ataque de tais fungos, e H. dulcis como a espécie mais predisposta ao ataque de tais agentes. Portanto, os efeitos estatisticamente significativos observados entre os ambientes estão relacionados com as características do microclima local de exposição da madeira, pois, segundo Melo et al (2010); Ribeiro et al (2014) e Carvalho et al (2016), normalmente no ambiente de floresta ocorre maior incidência e ação de organismos xilófagos. Essa ação provoca rápida decomposição da madeira exposta, consequentemente reduz sua durabilidade, impossibilitando ensaios mecânicos em tais corpos-de-prova (Figura 2A e B).…”

“…Legitimando tal informação, Mattos et al (2013), descrevem que esta situação acontece porque a madeira, quando exposta em diferentes estágios de deterioração, apresenta redução da compactação do material celulósico na parede celular, proporcionando perda de massa e da elasticidade da mesma. Panshin & De Zeeuw (1980) alegaram que madeiras mais densas ou menos porosas oferecem maior resistência ao apodrecimento por fungos, no entanto, essa situação não foi observada por Carvalho et al (2016), onde os autores avaliaram as mesmas amostras e espécies utilizadas neste estudo, obtendo a massa específica aparente a 12% de 0,67 g/cm³ para H. dulcis, 0,75 g/cm³ para E. robusta, 0,90 g/cm³ para E. tereticornis e 0,88 g/cm³ para E. dunnii, a qual teve maiores perdas de resistência.…”

Effect of thermal modification in the natural resistance of Eucalyptus grandis and Pinus taeda woods

“…In this case, the use of wood thermoretification processes can have the positive effect of protecting it. Carvalho et al (2016), when evaluating the PAF for more than one year, obtained mean temperature values of 21.8 °C and relative humidity (UR) of 75.3%, which resulted in a mean PAF of 10.1. For this work, the mean temperature was 20.5 °C and UR of 70.5%, similar to the result of the cited author; however, the mean PAF obtained for the present work was of 18.1, which can be explained by the higher number of rainy days, evidencing that the precipitation factor shows great influence on the probability of fungi occurrence.…”