Rapid growth rates and the accompanying reduced rotation ages of forest plantations have resulted in increased proportions of juvenile wood. Growing space markedly influences growth rate and may be manipulated by stand density management. The objective of this study was to evaluate the effect of stand density on the modulus of elasticity (MOE), modulus of rupture (MOR) and other selected properties of young (16–20 years) South African-grown Pinus patula lumber. Thirty-seven trees from two commercial stands were processed into 71 logs, cant sawn into lumber and tested for MOE, MOR, wood density and distortion. The first stand was planted at 1334 stems ha−1 and thinned to 827 stems ha−1 at age 11. The second stand was planted at 1667 stems ha−1 and was unthinned. Lumber from a previous study on 17 different commercial stands from more conventional (lower) stand density management regimes was also analysed using linear mixed-effect models. Only lumber from the 1667 stems ha−1 stand conformed to the requirements for structural use and had a considerably higher mean MOE of 8967 MPa compared to 7134 MPa for the 1334/827 stems ha−1 stand and 5556 MPa for the more conventional stands. MOR values were adequate for all stands. Unlike previous studies on other species, slenderness did not seem to have a profound effect on the MOE of the lumber from these P. patula trees. Stand density management therefore has the potential to increase lumber stiffness of P. patula and should be considered as a forest management intervention for wood quality improvement by saw-log growers in South Africa.

中文翻译：

---

林分密度管理对美洲松木材特性的影响

快速的生长速度和随之而来的人工林轮伐期的减少导致幼材比例增加。生长空间显着影响生长速度，可能受林分密度管理的影响。本研究的目的是评估林分密度对年轻（16-20 年）南非种植的松木的弹性模量 (MOE)、断裂模量 (MOR) 和其他选定特性的影响。来自两个商业林分的 37 棵树被加工成 71 根原木，不能锯成木材，并测试 MOE、MOR、木材密度和变形。第一个林分种植在 1334 茎 ha-1 并在 11 岁时间伐到 827 茎 ha-1。第二个林分在 1667 茎 ha-1 处种植并且未间伐。还使用线性混合效应模型分析了先前对来自更传统（较低）林分密度管理制度的 17 个不同商业林分的研究中的木材。只有 1667 杆 ha-1 支架的木材符合结构使用要求，并且与 1334/827 杆 ha-1 支架的 7134 MPa 和更传统的支架的 5556 MPa 相比，其平均 MOE 显着更高，为 8967 MPa。MOR 值适用于所有林分。与之前对其他物种的研究不同，细长似乎对来自这些 P. patula 树的木材的 MOE 没有深远的影响。因此，林分密度管理有可能增加 P. patula 的木材硬度，应被南非锯木种植者视为改善木材质量的森林管理干预措施。