Resumo

Silvicultural practices such as planting spacing are known to induce variation in wood quality, but the spatial variation of the wood traits along stems as a function of plantation density has been rarely reported, especially in fast-growing Eucalyptus plantations. Therefore, the objective of the present study was to generate a better understand about the effect of planting spacing on the variation of wood density, extractives and lignin content within Eucalyptus trees managed for pulp and paper industry. Four commercial clones planted in four planting spacing arrangements (3×1 m, 3×2 m, 3×3 m, and 3×4 m) were investigated at five-year-old. Wood discs (30 mm thick, defects free) were collected at six longitudinal points (base, 1.3 m from and at 25 %, 50 %, 75 % and 100 % of the commercial height) of the three Eucalyptus trees of each treatment, totaling 48 trees and 288 discs. Near infrared (NIR) models formerly calibrated for estimating wood density, extractive and lignin content were applied to NIR spectra collected radially at five equidistant points on the discs in order to estimate these wood properties along the tree trunks. The results revealed that the largest planting spacing arrangement (3×4 m) induced the formation of wood with greatest spatial variation, especially below 25 % of height. The spatial variation patterns vary according to genetic material. In terms of basic wood density, clone D exhibited the widest range of variation (52.7 kg m−3), whereas clone B showed the lowest values (39.6 kg m−3). Lignin content did not significantly differ between clones but varied significantly based on planting density. These results indicates that planting spacing affects the spatial variation in lignin content and wood density along the stem, depending on the genetic material.