Identificação da biodegradação de quatro espécies de madeiras tropicais por cupins subterrâneos e sua relação com as características tecnológicas.

Abstract

The resistance of woods of different species to the attack of biodegrading agents varies according to their characteristics, which affects their use and their potential effects on the environment in storage yards. The objective of this work was to relate the technological characteristics of wood with the degree and rate of biodegradation by underground termites of four tropical species. Four species were selected: timborana (Pseudopiptadenia suaveolens (Miq.) J. WGRIMES), pau amarelo (Euxylophora paraensis Huber), tamanqueira (Aegiphila integrifolia (Jacq.) Moldenke) and parapará (Jacaranda copaia (Aubl.) D.Don), two of them high density and two low density, in order to allow the analysis of the effect of other characteristics (chemical and anatomical) on biodegradation. The primary and secondary chemical components of the wood were determined, in addition to the anatomical and physical characterization of the species, as well as a bioassay of natural resistance with the soil termite (Nasutitermes sp.), lasting six weeks, with evaluation of mass loss and visual diagnosis of the specimens. The verification of the variation of the chemical composition of the specimens in relation to the experimental times was performed by an X-ray diffraction (XRD) analysis. The results show that the species presented different biodegradation rate, The species with the highest mean rate of mass loss was J. copaia (6.92%), the one with the lowest mean wear score (7.93) was the one with the lowest mean density (0.27g/cm3), the inverse was the one with E. paraensis presenting the highest mean values of wear score (10) and lower mass loss (0.45%) it was she who presented the second highest mean density value (0.68g/cm3), time was an important factor, because the results showed a progression in the rate of mass loss during the experiment, J. copaia showed the highest progression in mass loss being 2.13% in the first week and 15.20% in the sixth week, despite the distinct characteristics between species, the rate of mass loss may be equal depending on the time of biodegradation, A. integrifolia reached the rate of 2% in the fifth week, while P. suaveolens and J. copaia reached the same rate in four and one week respectively, the only exception was E. paraensis, which reached the maximum rate of 0.66% in the entire period studied, it can be verified that characteristics such as chemical composition and anatomical properties have greater influence in this process when comparing density. Therefore, it can be concluded that the differences in the chemical and anatomical compositions of the species affect the biodegradation process.