Reconstruction of root systems in Cryptomeria japonica using root point coordinates and diameters

Abstract

We developed simple algorithms for reconstructing tree root system architecture using only the root point coordinate and diameter, which can be systematically obtained without digging up the root systems. Root system architecture (RSA) is strongly related to various root functions of the tree. The aim of this study was to develop a three-dimensional (3D) RSA model using systematically obtained information on root locations and root diameters at the locations. We excavated root systems of Cryptomeria japonica and systematically obtained XYZ coordinates and root diameters using a 10-cm grid. We clarified the patterns of the root point connections and developed a reconstructed root system model. We found that the root diameters farther from the stump centre are smaller. Additionally, we found that the root lengths of the segments running between the base and the connected root point were smaller than those of other root segments, and the inner angle between the base and the stump and between the base and the connected root point was narrower than for the other pairs. The new RSA model developed according to these results had average accuracies of 0.64 and 0.80 for estimates of total volume and length, respectively. The developed model can estimate 3D RSA using only root point data, which can be obtained without digging up root systems. This suggests a wide applicability of this model in root function evaluation.

Preliminary Application of Ground-Penetrating Radar for Reconstruction of Root System Architecture in Moso Bamboo

“…To further improve the accuracy of the model, we need to study how best to recover missing root points in the RSA. Additionally, our model did not perform well when root points were relatively close together (Figure 14), a failure which is also consistently exhibited by the algorithms proposed by Wu et al [38] and Ohashi et al [39] for RSA reconstruction. A feasible approach to rectifying this problem may be to shorten the spacing of the GPR scan to obtain a more refined spatial distribution of root points.…”

“…Our model provides a more accurate score function than does the model established by Ohashi et al [39]. Their model only considered the distance between root points, the diameter of the root point, and the interior angle between root points.…”

“…This proved to be more conducive to obtaining the correct root point in the case of moso bamboo. Our model thus represents an optimization of that established by Ohashi et al [39]. In our model, the distance between survey lines is defined as the only constraint on the candidate root points, which means that our model exhibits high accuracy in determining root point connections.…”

“…However, their algorithm is not applicable to radar data collected from orthogonal grid scan lines. In addition, Ohashi et al [39] claimed that an algorithm they employed for the reconstruction of 3D RSA based on root point 3D coordinates (XYZ coordinates) and root diameter was suitable for use with GPR. However, this algorithm has not been validated with GPR data.…”

“…Root system topology, which refers to the pattern in which roots are interconnected, offers the potential for a more detailed understanding of the 3D RSA [49]. Therefore, it is preferable to use both spatial position and topology of the root system to obtain the complete 3D RSA [39]. GPR has been shown to accurately extract the spatial location of coarse roots [27,31,35,45], which provides a basis for new non-invasive, technological method for RSA reconstruction.…”