Measurement and visualization of the architecture of an adult tree based on a three-dimensional digitising device

Abstract

A method for the measurement of the three-dimensional (3D) architecture of trees is proposed. The method works at the shoot level and simultaneously describes the plant topology (i. e. branching pattern), the plant geometry (i. e. spatial co-ordinates of the tree entities) and the shoot morphology (i. e. number of shoots and fruits, basal diameter). The method combines a 3D digitising device (3SPACE FASTRAK, Polhemus) associated with software DiplAmi designed for digitiser control and data acquisition management. Plant images may be reconstructed from the data set by using the ray tracing software POV-Ray. The method was applied to the architectural description of a 20-year-old and 7-m-high walnut tree. Visual comparison between a tree photograph and an image synthesised from digitising is satisfactory. Information that can be derived from the data set at both the whole tree and the shoot levels is respectively illustrated from shoot morphology distributions and from spatial distribution of leaf area and fruit. Spatial distributions of leaf area and fruit are in agreement with previous results and hypotheses involving light gradients within the crown. Finally, methods for describing the 3D tree architecture are discussed as well as the feasibility of the method when applied to such a large tree.