Key message

Branch sizes and their vertical orientation increase progressively further up the lower stem to support a newly developing crown.

Abstract

Diameter at base, orientation, and height up the stem of live branches on the lower 5 m of tree stems were measured several times over 2.5–5.7 years of age in an experimental plantation of blackbutt (Eucalyptus pilularis) in sub-tropical eastern Australia. Stocking density at planting varied over 816–1667 stems ha^-1 and rectangularity of planting (ratio of distance between rows to distance between trees within rows) over 1–6. Tree stem diameters, heights and crown dimensions were also measured. The height above ground at which branches emerged from the stem was a primary factor determining their growth; the higher they were, the greater was their diameter and the more vertical their orientation. This was believed to reflect both a need for newer branches to grow larger than older branches, to support greater amounts of foliage as the crowns expanded towards full size, and for branches to be better oriented to seek sunlight as the crowns of surrounding trees also expanded. Secondary factors determining branch size were tree size and spacing between trees, factors that are likely to interact with each other. Larger trees tended to have larger branches, to support more leaf weight in larger crowns. The direction of emergence of branches from stems seemed little affected by tree or stand characteristics at these early stages of tree development. The results did not suggest any need to modify existing pruning regimes that have been developed for fast-growing eucalypt plantations in Australia.

中文翻译：

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在亚热带澳大利亚实验性桉树人工林的早期生长过程中控制个体分支发育的因素

关键信息

分支的大小及其垂直方向在下茎上进一步逐渐增加，以支撑新近发育的树冠。

抽象

直径为基础，方向和高度达活枝在下5米树的茎茎在blackbutt（的实验种植园多次测量了2.5-5.7岁桉树pilularis亚热带澳大利亚东部）。种植时的种群密度在816–1667茎ha ^{-1之间变化}和种植的矩形度（行间距离与行内树木之间的距离之比）超过1-6。还测量了树木的茎直径，高度和树冠尺寸。茎部出现分支的地面高度是决定其生长的主要因素。它们越高，它们的直径就越大，并且其取向越垂直。人们认为，这既反映了新的树枝要比旧的树枝长得更大，需要在冠向全尺寸扩展时支撑更多的叶子，又随着周围树木的冠也扩展以更好地寻找阳光的需求。 。确定分支大小的次要因素是树的大小和树之间的间距，这是可能相互影响的因素。较大的树往往有较大的树枝，以支持更大的树冠更大的叶子重量。在树木发育的这些早期阶段，茎秆出现的方向似乎不受树木或林分特征的影响。结果表明，没有必要修改为澳大利亚快速生长的桉树人工林开发的现有修剪制度。