Planting spacing plays an important role in tree growth and wood formation. Thus, the aim of this study was to determinate how planting spacing and genetic material affect the radial variation of basic density and chemical composition of wood. The sampling of this study was based on 4 clones of Eucalyptus urophylla × Eucalyptus grandis at 5 years of age planted in four spacings (3 × 1, 3 × 2, 3 × 3 and 3 × 4 m). To determine the basic density (BD), extractive (EXT) and lignin (LT) content, wood discs were removed at breast height, which were sectioned in three radial positions (pith, intermediate and sapwood). The results showed that genetic material, planting spacing and radial position affected the values of BD, EXT and LT content. The BD and EXT content tended to increase with increased planting spacing, while the LT content tended to decrease. In relation to the radial variation, the basic density showed an increase in the pith-bark direction, while the EXT content showed a decrease in this direction. For LT, no significant difference was observed in the pith-bark direction. In general, the largest planting spacings promoted the highest rates of variation of the properties studied.

中文翻译：

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种植间距影响快速生长的年轻桉树人工林木材基本密度和化学成分的径向变化

种植间距对树木生长和木材形成起着重要作用。因此，本研究的目的是确定种植间距和遗传物质如何影响木材基本密度和化学成分的径向变化。本研究的采样基于 4 个克隆尾叶桉×巨桉5年生时按四种行距种植（3×1、3×2、3×3和3×4m）。为了测定基本密度 (BD)、浸出物 (EXT) 和木质素 (LT) 含量，在胸高处取出木盘，将其在三个径向位​​置（髓心、中间和边材）进行切片。结果表明，遗传物质、株行距和径向位置影响BD、EXT和LT含量值。BD和EXT含量随行距增大呈增加趋势，而LT含量则呈下降趋势。相对于径向变化，基本密度沿髓皮方向增加，而EXT含量沿该方向减少。对于LT，在髓皮方向没有观察到显着差异。一般来说，