Below- and aboveground architecture of Androstachys johnsonii prain: topological analysis of the root and shoot systems

Abstract

Aim: This study aimed to analyse the topological branching pattern, area-preserving branching, and fractal branching pattern (self-similarity) of the root and shoot systems of 93 Androstachys johnsonii trees with diameter-at-breast heights of 5–32 cm. Methods: Topological parameters were calculated. Results: Visual analysis indicated herringbone-like branching pattern for both the root and shoot systems. However, the topological index (TI) and topological trend (TT) suggested otherwise. This discrepancy was attributed to the fact that A. johnsonii has multiple laterals per stem/taproot node, suggesting that the topological indexes (TI and TT) might yield biased conclusions regarding the branching pattern when the main axis has multiple laterals per node. Hence, modified topological index (TIM) that could be applied in the cases of multiple laterals per node while conserving the values of TI for cases with one lateral per node was developed; the modified index was more efficient and realistic than TI. Conclusion: The area preserving branching was confirmed for each stem node confirming thus, the self-similar branching. For the root system, the area-preserving branching was only confirmed for the first node; therefore, self-similarity was not confirmed.