Densidade básica e retratibilidade da madeira de clones de três espécies de Eucalyptus

摘要

Among the planted forests that supply the national wood industry, the genus Eucalyptus has become the most important, due to its fast growth, ease of large scale planting and variability of wood use. The generation of new hybrids and clones is a reality in the national practice of silviculture, and there is great interest currently in finding genetic improvements, mainly for higher volumetric gains and resistance in rough conditions of planting, such as pest attacks, periods of drought, low soil fertility, etc. The basic density is one of the most important physical properties of wood because it relates directly to other properties, including the anisotropic shrinkage. Such properties indicate the rational use of a species in a certain wood product. The aim of this work was to determine the basic density and the anisotropic shrinkage of five wood clones for each one of the following species: Eucalyptus saligna, Eucalyptus grandis and Eucalyptus dunnii . Clone 5 of Eucalyptus saligna presented the highest basic density (0.56 g/cm3) and was the most dimensionally instable. Of all the species, there was only a direct relation among basic density, maximum volumetric shrinkage and maximum volumetric shrinkage coefficient in this clone. Considering maximum volumetric shrinkage as the criterion, clone 3 was the most dimensionally stable. Clones 2 and 3 of Eucalyptus grandis presented the least and the highest basic density, respectively, with 0.40 and 0.49 g/cm3. It was not possible to distinguish among clones 1, 3 and 4 in terms of dimensional stability, and considering maximum volumetric shrinkage coefficient as the criterion, clone 5 was the most dimensionally instable. For Eucalyptus saligna and Eucalyptus dunnii it was not possible to distinguish which clone presented the least basic density. Clone 3 of Eucalyptus dunnii presented the highest basic density (0.65 g/cm3) and considering maximum volumetric shrinkage coefficient as the criterion, it was the most dimensionally instable clone, whereas considering maximum volumetric shrinkage, clone 1 was the most stable. Eucalyptus grandis presented the least basic density and was the most stable, while Eucalyptus dunnii presented the highest basic density and was the most dimensionally instable.