Architecture characterization of orchard trees for mechanical behavior investigations

Abstract

Abstract Background Statistical analysis of root architectural parameters is necessary for development and exploration of root structure representations and their resulting anchorage properties. Three-dimensional (3D) models of orchard tree root systems, Lovell (from seed, prunus persica), Marianna (from cutting, prunus cerasifera), Myrobalan (from cutting, also prunus cerasifera), that were extracted from the ground by vertical pullout are reconstructed through photogrammetry, and then skeletonized as nodes and root branch segments. Combined analyses of the 3D models and skeletonized models enable detailed examination of basic bulk properties and quantification of architectural parameters divided into simple root segment classifications— trunk root, main lateral root, and remaining roots. Results The patterns in branching and diameter distributions show significant difference between the trunk and main laterals versus the remaining lateral roots. In general, the branching angle decreases with branching order. The main lateral roots near the trunk show significant spreading while the lateral roots near the end tips grow roughly parallel to the parent root. For branch length, the roots branch more frequently near the trunk than further from the trunk. 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 branching angle, and branch length and thickness gradient can be described using lognormal and exponential distributions, respectively. Conclusions Statistical measurements of root system architecture upon hierarchy provide a basis for representation and exploration of root system structure. This unique study presents data to characterize mechanically important structural roots, which will help link root architecture to the mechanical behaviors of root structures.