ABSTRACT Branch development in trees 1.6–5.7 years after planting was studied in a plantation experiment involving Eucalyptus pilularis in subtropical eastern Australia. The experiment compared stocking densities at planting in the range of 816–1667 stems ha−1 and rectangularities of tree spacing in the range of 1–6. Branch diameters at their bases were measured on the lowest 5 m of the stems of trees judged likely to yield sawn timber of high quality at final harvest. Neither stocking density nor rectangularity had substantial effects on branch numbers or diameters. Particular interest was paid to the presence of branches with diameters in excess of 2.5 cm that might produce knots large enough to degrade the quality of sawn timber. Such branches developed on lower stems between 2–4 years of age. An average of nearly five such branches was found on more widely spaced trees, reducing to 2–3 on more closely spaced trees. The results confirmed other work suggesting that pruning of high-quality eucalypt plantations should start near 2–3 years of age to both limit the development of large branches and restrict the size of knotty cores in logs. There was no evidence that changing the rectangularity of spacing to 3 or a little more, from the more normal practice of close to square, would affect such pruning regimes: increasing the distance between rows can reduce establishment and harvest costs and allow easier access for silvicultural operations.

中文翻译：

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树间距对澳大利亚亚热带桉树试验人工林早期生长过程中分枝大小发育的影响

摘要 在澳大利亚东部亚热带地区的一项涉及毛桉的种植园实验中，研究了种植后 1.6-5.7 年树木的枝条发育。该实验比较了种植时在 816-1667 茎 ha−1 范围内的放养密度和树间距在 1-6 范围内的矩形度。根部的分枝直径是在被判断为可能在最终收获时产出高质量锯材的树干的最低 5 m 处测量的。放养密度和矩形度都对分枝数或直径没有实质性影响。人们特别关注直径超过 2.5 厘米的树枝的存在，这些树枝可能会产生足够大的结节，从而降低锯材的质量。这些分支在 2-4 岁之间在较低的茎上发育。在间距较宽的树上平均发现近 5 个这样的分支，在间距较近的树上减少到 2-3 个。结果证实了其他工作，即高质量桉树人工林的修剪应在 2-3 年左右开始，以限制大树枝的发育并限制原木中多节核的大小。没有证据表明将间距的矩形度从更接近正方形的更正常做法改为 3 或更大一点会影响这种修剪制度：增加行距可以降低建立和收获成本，并使造林更容易进入操作。结果证实了其他工作，即高质量桉树人工林的修剪应在 2-3 年左右开始，以限制大树枝的发育并限制原木中多节核的大小。没有证据表明将间距的矩形度从更接近正方形的更正常做法改为 3 或更大一点会影响这种修剪制度：增加行距可以降低建立和收获成本，并使造林更容易进入操作。结果证实了其他工作，即高质量桉树人工林的修剪应在 2-3 年左右开始，以限制大树枝的发育并限制原木中多节核的大小。没有证据表明将间距的矩形度从更接近正方形的更正常做法改为 3 或更大一点会影响这种修剪制度：增加行距可以降低建立和收获成本，并使造林更容易进入操作。