Architecture characterization of orchard trees for mechanical behavior investigations

Abstract

Characterizing the architecture of tree root systems is essential to advance the development of root-inspired anchorage in engineered systems. This study explores the structural root architectures of orchard trees to understand the interplays between the mechanical behavior of roots and the root architecture. Full three-dimensional (3D) models of natural tree root systems, Lovell, Marianna, and Myrobalan, that were extracted from the ground by vertical pullout are reconstructed through photogrammetry and later skeletonized as nodes and root branch segments. Combined analyses of the full 3D models and skeletonized models enable a detailed examination of basic bulk properties and quantification of architectural parameters. While the root segments are divided into three categories, trunk root, main lateral root, and remaining roots, the patterns in branching and diameter distributions show significant differences between the trunk and main laterals versus the remaining lateral roots. In general, the branching angle decreases over the sequence of bifurcations. The main lateral roots near the trunk show significant spreading while the lateral roots near the ends grow roughly parallel to the parent root. For branch length, the roots bifurcate more frequently near the trunk and later they grow longer. Local thickness analysis confirms that the root diameter decays at a higher rate near the trunk than in the remaining lateral roots, while the total cross-sectional area across a bifurcation node remains mostly conserved. The histograms of branc;/.hing angle, and branch length and thickness gradient can be described using lognormal and exponential distributions, respectively. This unique study presents data to characterize mechanically important structural roots, which may help link root architecture to the mechanical behaviors of root structures.

Keywords

Bio-inspired foundation / Root architecture / 3D root model / Skeleton / Statistical variation / Mechanical pullout test

Funding

This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (RS-2024- 00340851) and the Engineering Research Center Program of the National Science Foundation (NSF) under NSF Cooperative Agreement EEC-1449501. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the NSF.

CRediT authorship contribution statement

Min-Kyung Jeon: Writing - review & editing, Writing - original draft, Validation, Methodology, Investigation, Formal analysis, Data curation. Matthew Burrall: Writing - review & editing, Visualization, Validation, Software, Resources, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Tae-Hyuk Kwon: Writing - review & editing, Validation, Supervision, Resources, Project administration, Investigation, Funding acquisition, Conceptualization. Jason DeJong: Writing - review & editing, Writing - original draft, Visualization, Supervision, Resources, Project administration, Methodology, Funding acquisition, Conceptualization. Alejandro Martinez: Writing - review & editing, Writing - original draft, Supervision, Resources, Investigation, Funding acquisition.

Declaration of Competing Interest

Alejandro Martinez is the Associate Editor of Biogeotechnics, Jason T. DeJong is an Editorial Board Member of Biogeotechnics, they were not involved in the editorial review or the decision to publish this article. The other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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