Qualidade da madeira de clones híbridos de Corymbia torelliana e Corymbia citriodora para produção de carvão vegetal de uso siderúrgico

Abstract

The quality of wood is one of the main assumptions for choosing genetic materials in forests dedicated to the production of charcoal for steel use. The characteristics of wood are decisive in the cost-benefit relationship at several stages of the production chain, from harvesting to the production and use of charcoal in blast furnaces. Considering the importance of evaluating hybrid clones of Corymbia torelliana and Corymbia citriodora at different stages of the charcoal production chain, the objectives of this thesis were: i) to evaluate the variability of density, bark, heartwood and sapwood contents, ii) the relationships anatomical characteristics of wood and its influence on the natural drying of wood in logs and, iii) analyze the characteristics of tree growth, wood quality and the properties of charcoal for steel use. Four hybrid clones of C.torelliana and C.citriodora and one clone of E.urophylla were studied as a comparison parameter, which is the most used genetic material in the production of charcoal, all at seven years of age, planted in Bom Despacho – MG Growth characteristics, wood quality (anatomical, physical and chemical) and charcoal quality were determined. Statistical techniques such as multiple comparison tests, principal component analysis and regression models were used, which were able to distinguish Corymbia clones from E. urophylla and, among them, identify the variables of greatest influence for these stratifications. It was identified that, anatomically, the hybrids of C.torelliana and C.citriodora differ from E. urophylla mainly because they have smaller vessel areas, fibers 7% shorter, 16% less wide, with 45% smaller lumen diameter and 16% thicker than E. urophylla clone 05. Wood radii from hybrids of C. torelliana and C. citriodora were 25% lower and 17% more frequent than those of wood from E. urophylla. These characteristics allowed lower water loads and greater agility in the drying process. The hybrids of C.torelliana and C.citriodora show greater variation between trees and within trees in wood properties. It was found that the best points for sampling the trees to determine the density and percentages of bark, sapwood and heartwood are different for each genetic material, since the density variation profiles in the bark-bark and base-top directions are different for each clone. The hybrid clones of C. torelliana and C. citriodora differ from E. urophylla in terms of growth characteristics, wood quality and charcoal properties, in different magnitudes, however, the growth characteristics and wood quality provide greater distance between the genera than the characteristics of charcoal. Knowing the differences between the characteristics of Corymbia and E. urophylla hybrids enables better decision-making for choosing genetic materials that favor the charcoal production process.