Yang, Wanxin; (2025) New Ways to Exploit 3D Terrestrial Laser Scanning for Tree Architecture and Function. Doctoral thesis (Ph.D), UCL (University College London).

Text Wanxin Yang - PhD Thesis.pdf - Accepted Version Access restricted to UCL open access staff until 1 February 2026. Download (59MB)

Abstract

Tree architecture, including morphology and topology, plays a crucial role in growth, reproduction, and adaptability to environmental conditions. Accurate quantification of tree architectural traits enables the exploration of structural-functional relationships, offering insights into the ecological roles and adaptive mechanisms of trees in forest ecosystems. Terrestrial laser scanning (TLS) provides a non-destructive method for characterising 3D tree architecture. However, the accuracy and precision in retrieving tree architectural traits remains constrained by current TLS approaches. Most existing 3D tree reconstruction methods focus on retrieving total volume at tree scale for aboveground biomass (AGB) estimation. These methods make various structural assumptions about tree shape to optimise volume estimation, making any derived structural information dependent on these assumptions and unsuitable for addressing architectural questions without circularity. Additionally, there is a lack of publicly available validation datasets to quantify uncertainties in estimated architectural properties from different reconstruction approaches. The main objective of this thesis is to develop an automated method for deriving detailed tree architectural traits from TLS data across all branching levels, extending TLS applications beyond volume estimation to provide detailed branching network information with minimal a priori structural assumptions. A validation dataset encompassing both morphological and topological properties of diverse tree species, sizes, and shapes was established to evaluate the approach. The proposed method provides fine-scale branching network information, offering new insights into tree architecture and function. Applied to 603 trees from tropical, temperate, and urban forests, the derived architectural traits are used to test structure-related metabolic scaling theories. The results indicate that while the West, Brown, and Enquist (WBE) model is useful for general predictions, it does not fully capture architectural diversity across all branching levels. The proposed method provides the TLS ecology community with a scalable solution for automating tree architecture reconstruction, with significant potential for integration in large-scale ecological studies related to tree architecture.

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