Influência da idade na proporção de cerne e na densidade da madeira de Tectona grandis L. F.

Abstract

The wood from Tectona grandis stands out in the world market due to the aesthetic characteristics and multiplicity of applications. The teak plantations introduced in Brazil, provide to the market trees with desired commercial dimensions in a short period, but with higher proportions of sapwood and juvenile wood when compared to teak wood from their place of origin. Thus, this study aims to evaluate the effect of age on the proportion of heartwood and on the density of teak wood. The wood used in this research comes from a commercial plantation where 12 trees of clonal and seminal origin were collected at ages of 5, 10, 15 and 20 years, in the field, discs were taken from the base, middle, and top regions of the tree. Along the tree stem, the proportions of bark, sapwood, heartwood, pith were measured, and the eccentricity of the pith and basic density were determined. Diametric baguettes were obtained from the base discs to analyze the wood apparent density and to demarcate the transition wood from juvenile to adult, using the X-ray densitometry technique. There was an increase in the percentage of heartwood and decrease in the percentage of sapwood and bark, according to the age increase. The clonal materials (5C and 10C) had the lowest values of pith eccentricity. The woods in this study are classified as having moderate basic density and present an average basic density of 0.53 g.cm- ³. Diametric profiles by X-ray densitometry indicate an increase in apparent density on the direction of pith to bark, regardless of the age evaluated. The 5-year-old wood presented the highest value of apparent density and from 10 years of age, there was a tendency for the apparent density rise as the age of the trees increased. At all ages evaluated, the wood is mostly composed of juvenile wood, and only the treatments of 15 and 20 years showed heartwood with adult wood, with transition wood at the 11th year. It's concluded that the evaluated commercial plantation needs to increase the cutting period to have a better development of the plantation and consequently an increase in the value of the wood.