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.

众所周知，种植间距等造林实践会引起木材质量的变化，但沿茎的木材性状的空间变化作为种植密度的函数却很少报道，特别是在快速生长的桉树种植园中。因此，本研究的目的是更好地了解种植间距对纸浆和造纸工业用桉树木材密度、提取物和木质素含量变化的影响。以四种株距排列（3×1 m、3×2 m、3×3 m 和 3×4 m）种植的 4 个商业无性系在 5 年生时进行了调查。在每个处理的三棵桉树的六个纵向点（基部，距离商业高度 1.3 m，在商业高度的 25%、50%、75% 和 100% 处）收集木盘（30 mm 厚，无缺陷），总计48 棵树和 288 个圆盘。以前为估计木材密度、提取物和木质素含量而校准的近红外 (NIR) 模型应用于在圆盘上五个等距点径向收集的 NIR 光谱，以便估计沿树干的这些木材特性。结果表明，最大的种植间距布置（3×4 m）诱导了空间变异最大的木材的形成，特别是在25%高度以下。空间变异模式根据遗传物质而变化。就基本木材密度而言，无性系D表现出最大的变化范围（52.7 kg m ^-3 ），而无性系B则表现出最低值（39.6 kg m ^-3 ）。木质素含量在克隆之间没有显着差异，但根据种植密度而显着变化。 这些结果表明，种植间距会影响沿茎的木质素含量和木材密度的空间变化，具体取决于遗传物质。