In Situ Detection of Tree Root Systems under Heterogeneous Anthropogenic Soil Conditions Using Ground Penetrating Radar

Abstract

Tree roots can cause damage to surface and subsurface infrastructure. Hence, timely detection of root system architecture (RSA) is needed to reduce conflict between trees and man-made facilities. Because excavation is expensive and often restricted, noninvasive detection of RSA by ground penetrating radar (GPR) is a promising technique. Although several studies have proven the ability of GPR for RSA detection, the problem of distinguishing roots from unwanted reflections at urban test sites with heterogeneous, silty, clayey, or stony soil has not yet been fully solved. This study assessed the performance of GPR for in situ detection of RSA from a plane tree (Platanus acerifolia) and a buckeye (Aesculus hippocastanum) in urban heterogeneous multilayered soil using shielded 250-MHz antennas. Repeated manual hyperbola selections were performed, extracting the three-dimensional (3D) coordinates, which were visualized in top view to reveal connected structures. Unwanted selections were manually filtered by internal confirmation using depth slices from 3D radargram interpolations. Root indications were retraced in the field and validated by vacuum excavation. At our test site, the suggested approach was suitable for detecting the lateral positions of roots with diameters between 1 and 4 cm at depths of 17 to 70 cm, despite unfavorable substrate. Moreover, the assumed depth ranges were correct for both trees, and the main depth characteristics were fairly precisely projected. The rapid and cost-effective protocol allows minimal interventions and opens the door for similar applications in urban and nonurban land uses.