Root morphologies can dominate the plant growth to absorb the water and nutrients. It is also required for the patterns of root morphology in the plant adaptation to ecological environments. However, some challenges are posed from the invisibility of plant root systems buried underground during the quantitative analysis of root morphologies. This study aims to achieve the non-destructive interpretation of root morphologies and root biomass. A quantitative analysis was also proposed on the root morphologies and root biomass using ground penetrating radar (GPR). A simple approach was provided to non-destructively reveal the growth form and spatial distribution of underground tree roots. The nine-year-old Chinese ash tree (Fraxinus chinensis Roxb.) was taken as the research subject in northern China. Initially, a 900 MHz GPR system was employed to conduct a square grid scan of the root system. A GPR C-scan data volume was generated with the root morphologies. Subsequently, the vertices of the root system reflection hyperbola in each B-scan image were extracted to spatially locate the root systems within the C-scan data volume. Additionally, the total propagation time of radar waves through the root systems was derived from the A-scan images intersecting the root system hyperbolic vertices. The root system diameter was then estimated after operation. After that, the localization of root system was facilitated to reconstruct the three-dimensional (3D) spatial distribution of the root system architecture (RSA). Finally, the root systems were modeled as the frustum-of-a-cone, in order to quantitatively analyze morphological characteristics, such as the length, surface area, volume, and spatial growth angles. A relationship model was established between the root volume and biomass. Non-destructive estimation of root biomass was realized using root volume characteristics. The feasibility and accuracy of the quantitative analysis was also validated for the root morphologies and root biomass. The whole root excavation was evaluated after validation. The research results indicated that: (1) The GPR was effectively detected the buried root systems, with a correct identification rate of 64.2%, primarily located at the depths of 0.1 to 0.4 m (76.9%); (2) The accurate locating root system was achieved in the vertices of the reflection hyperbola from the GPR C-scan data volume. There was an average root point localization error of 15.8%; (3) The diameter of root system was effectively estimated, according to the total propagation time of radar waves, indicating an average estimation error of 26.4%; (4) The quantitative analysis was feasible on the root morphologies using the frustum-of-a-cone model. The total length, total surface area, and total volume of the RSA reconstructed by GPR were 786.5 cm, 12 588.9 cm², and 19 969.9 cm³, respectively, with the estimation accuracies of 66.77%, 80.72%, and 93.84%, respectively; (5) The root volume was effectively represented the root biomass, with an estimated biomass of 0.131 g/cm² and an accuracy rate of 76.09%. The root-soil mechanics can also be expected to non-destructively monitor the root growth. Additionally, the dynamic assessment of root biomass accumulation was enhanced to understand the root growth and survival mechanisms. The great contribution are gained for the ecological adaptation strategies of the roots in complex environments. The finding can also provide the technical support for the forestry production and ecological protection.

Root system architecture (RSA) is pivotal for comprehending the ecological adaptation strategies and resource acquisition mechanisms of urban flora, playing a vital role in soil stability, carbon sequestration, and ecosystem sustainability. However, the non-destructive detection and precise three-dimensional (3D) reconstruction of RSA within urban environments remain challenging. In this study, a non-destructive reconstruction method utilizing ground-penetrating radar (GPR) technology was developed to achieve 3D reconstruction and visualization of RSA, with the goal of advancing the intelligent construction and precise ecological management of urban forest parks. Field-based GPR surveys of a 9-year-old triploid poplar were conducted using a square grid and concentric circular scanning scheme. A 3D data volume (C-scan) was constructed from two-dimensional (2D) profiles, and the spatial distribution of RSA was reconstructed using instantaneous amplitude analysis. The method was validated by comparing the results with actual root structures in sandy loam environments. The research results of the 1600 ​MHz GPR under the square grid scanning scheme show that extracting the instantaneous amplitude isosurface of GPR can effectively reflect the spatial distribution of roots with diameters greater than 1 ​cm within a depth of 0.4 ​m subsurface. The accuracy of RSA reconstruction can reach 89 ​%. The results demonstrate the applicability of the proposed method for non-destructive environmental monitoring in urban forest parks, showing significant potential for the large-scale detection and reconstruction of subsurface root systems. This research provides a novel approach for RSA reconstruction with significant implications for urban ecosystem management, soil conservation, and climate resilience research. The method enhances our capability to monitor the growth and adaptation of urban roots, laying the groundwork for the large-scale, non-destructive analysis of RSA.