Validation of L-Architect model for balsam fir and black spruce trees with structural measurements

Abstract

The fine reconstruction of tree structure provides important information that is relevant to forest ecological processes and may be linked to wood quality attributes. Terrestrial laser scanners (TLS) provide detailed and accurate 3-D data and have the potential to enhance forest inventories with fine-scale information on structure. However, in forests, TLS data are limited by the effects of object occlusion and wind. Therefore, adequate tree reconstruction is not possible. In previous studies, we used the architectural model L-Architect (LiDAR data to tree Architecture) to overcome the limitations of TLS to characterize the 3-D tree structure. In this study, L-Architect was validated using structural measurements for two coniferous species found in Newfoundland (Canada), namely, balsam fir (Abies balsamea) and black spruce (Picea mariana). The model reproduced realistic tree structures using TLS data and allometric relationships to define the total amount of foliage following two main steps: branch growth and addition of foliage within the crown. Results from L-Architect were compared with measurements of branching structure from the main stem (angle of insertion, length, and diameter) and vertical distribution of foliage indicated by the shoot vertical distribution for six sampled trees. Averaged normalized root-mean square errors of 21%, 20%, 25%, and 21% were obtained for branch diameter, branch length, angle of branch insertion, and vertical distribution of foliage, respectively.