Variação espacial das fibras de eucalipto considerando a estrutura dos anéis anuais de crescimento

Abstract

Fiber properties vary along the tree stem and these variations are related to the activities of the apical meristems and vascular cambium, where their understanding helps in the best wood utilization. There are several studies regarding the pattern of dimensional variation of fibers along the stem in the radial and longitudinal directions, however, the vast majority do not consider the structure of the tree’s annual growth rings. Thus, this research aimed to determine the fiber’s pattern of dimensional variation along the stem, in addition to estimating the general model of the variation pattern based on information from the tree’s annual growth rings. Two hybrid clones from the crossing of E. urophylla x E. grandis with 10 years of age that underwent thinning at 4 years of age were used for the study, being sampled two trees per clone. In the selected trees, discs were removed in different longitudinal positions: 0.30 m, 1.30 m and every two meters up to 23.3 m in height. After the preparation of the discs, the growth rings were identified, sectioned and sampled for fiber individualization. Nicholls and Dadswell's method was used for maceration. Twenty fibers were measured, by longitudinal sampling position, with the aid of an optical microscope using the program Dinocapture 2.0. Linear regression models were used to obtain the pattern of variation by fiber characteristic in the radial and longitudinal directions along the stem. The selection of the best model was based on the significance of the regression and its coefficients, adjusted coefficient of determination, coefficient of variation of the model and the graphical analysis of the residues. It was observed that longitudinally, within the annual growth rings, the fiber’s dimensions and their indicative quality indexes did not present a well-defined variation pattern. The fiber’s length, wall thickness, wall fraction and Runkel index tended to increase in the marrow bark direction, while the lumen diameter and flexibility coefficient decreased. It was not possible to define a single model to predict the variation patterns per annual growth ring.