1. Quantifying whole branch architecture is critical to understanding tree function, for example, branch surface area controls woody gas exchange. Yet, due to measurement difficulty, branch architecture of small diameter branches (e.g. <10 cm ) is modelled, subsampled or ignored. Methods that use terrestrial laser scanning (TLS) are now being widely applied to analyse tree and plot-level tree architecture; however, resolving small diameter branches in-situ remains a challenge.
2. Currently, it is suggested that accurate reconstruction of small diameter branches can only be achieved by harvest and measurement in controlled conditions. Here we present a new TLS workflow for rapid and accurate reconstruction of complete branch architecture from harvested branches. The workflow sets out scan configuration, post-processing (including a novel reflectance filter) and fitting of quantitative structure models (QSM) to reconstruct topologically coherent branch models. This is demonstrated on 595 branches (scanned indoors to negate the impact of wind) and compared with 65 branches that were manually measured (i.e. with measuring tape and callipers).
3. Comparison of a suite of morphological and topological traits reveals a good agreement between TLS-derived metrics and manual measurements where RMSE (%RMSE) for total branch length = 0.7 m (10%), volume = 0.09 L (43%), surface area = 0.04 m² (26%) and N tips = 6.4 (35%). Scanning was faster and invariant to branch size compared with manual measurements which required significantly more personnel time. We recommend measuring a subsample of tip widths to constrain the QSM taper function as the TLS workflow tends to overestimate tip width.
4. The workflow presented here allows for a rapid characterisation of branch architecture from harvested branches. Increasing the number of branches analysed (e.g. many branches from a single tree or branches from many species globally) could allow for a comprehensive analysis of the ‘missing link’ between the leaves and larger diameter branches.

中文翻译：

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地面激光扫描从收获的树枝重建树枝结构

1. 量化整个树枝结构对于理解树木功能至关重要，例如，树枝表面积控制木质气体交换。然而，由于测量困难，小直径分支（例如<10 cm ）的分支结构被建模、子采样或忽略。使用地面激光扫描 (TLS) 的方法现在被广泛应用于分析树和地块级树结构；然而，原位解析小直径分支仍然是一个挑战。
2. 目前，建议小直径树枝的精确重建只能通过在受控条件下的收获和测量来实现。在这里，我们提出了一种新的 TLS 工作流程，用于从收获的分支中快速准确地重建完整的分支架构。该工作流程规定了扫描配置、后处理（包括新型反射过滤器）和定量结构模型 (QSM) 的拟合，以重建拓扑相干分支模型。这在 595 根树枝上得到证明（在室内扫描以消除风的影响），并与手动测量的 65 根树枝（即使用卷尺和卡尺）进行比较。
3. 一组形态和拓扑特征的比较揭示了 TLS 衍生指标与手动测量之间的良好一致性，其中总分支长度的 RMSE (%RMSE) = 0.7 m (10%)，体积 = 0.09 L (43%)，表面积= 0.04 m ² (26%) 和N尖端 = 6.4 (35%)。与需要更多人员时间的手动测量相比，扫描速度更快且不受分支大小的影响。我们建议测量尖端宽度的子样本以限制 QSM 锥度函数，因为 TLS 工作流程往往会高估尖端宽度。
4. 此处介绍的工作流程允许从收获的分支中快速表征分支架构。增加分析的树枝数量（例如，来自一棵树的许多树枝或来自全球多个物种的树枝）可以对叶子和较大直径树枝之间的“缺失环节”进行全面分析。