Abstract
This study evaluated the quality of heartwood and sapwood from mature trees of three species of Eucalyptus, by means of the qualification of their proportion, determination of basic and apparent density using non-destructive attenuation of gamma radiation technique and calculation of the density uniformity index. Six trees of each species (Eucalyptus grandis - 18 years old, Eucalyptus tereticornis - 35 years old and Corymbia citriodora - 28 years old) were used in the experimental program. The heartwood and sapwood were delimited by macroscopic analysis and the calculation of areas and percentage of heartwood and sapwood were performed using digital image. The uniformity index was calculated following methodology which numerically quantifies the dispersion of punctual density values of the wood around the mean density along the radius. The percentage of the heartwood was higher than the sapwood in all species studied. The density results showed no statistical difference between heartwood and sapwood. Differently from the density results, in all species studied there was statistical differences between uniformity indexes for heartwood and sapwood regions, making justifiable the inclusion of the density uniformity index as a quality parameter for Eucalyptus wood.
Highlights
Wood is a heterogeneous material formed by a set of cells with specific properties to perform the main functions of water conduction, storage of biochemicals and mechanical support of the plant body
Eucalyptus tereticornis (35 years old) provided by PREMA Tecnologia e Comécio Ltda are from Casa Grande Farm, Corumbataí, São Paulo State, Brazil (22o13’6’’ S; 47o31’21’’ W)
All the disks were peeled, planed in a lathe, and sanded with orbital sander to acquire uniform thickness (20 mm for the disk to quantification of heartwood and sapwood and 30 mm for the disk to attenuation gamma radiation technique); the disks were stored to equilibrium in a climate-controlled room under 65% relative humidity and 21 oC
Summary
Wood is a heterogeneous material formed by a set of cells with specific properties to perform the main functions of water conduction, storage of biochemicals and mechanical support of the plant body. Wood of most trees can be divided into two distinct regions in terms of their physiological activity: sapwood and heartwood These regions are identified in many species, their occurrence, properties and color can vary (Hillis 1987). In certain species, despite the existence of heartwood, there are little or almost no visually detected differences between heartwood and sapwood colors In such cases, identification requires the analysis of differences in the chemical level as a difference in pH between the sapwood and heartwood (Hillis 1987, McKimm 1985, Campbell et al 1990, Winandy and Morrell 1993, Clarke et al 1997) or the observation of anatomical features - tyloses may be used to distinguish heartwood from sapwood but only in species where such features are closely associated with heartwood formation (Bamber and Fukazawa 1985). The application of X-ray densitometry can be extremely useful to identify the sapwood - heartwood boundaries, based on different wood properties and levels of X-ray attenuation (Tomazello Filho et al 2008)
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