Criteria for mapping and estimation root systems using ground penetrating radar by the example of the European spruce

Abstract

This study discusses about approaches to using ground penetrating radar (GPR) techniques to characterize tree roots and to monitor their conditions in urban environments. For this purpose, our research was to map and determine the reliability of the root system of trees evaluating in their natural occurrence using the GPR method. As an object of research, a separate European spruce (Picea abies (L.) H. Karst.) was selected, under which a testing area measuring 4 × 4 m was laid. To increase the detail, the field survey was performed with a GPR with a high-frequency antenna unit of 1,700 MHz. The influence of the observation networks on the GPR data on root architectonics was analyzed depending on their spatial orientation. Thus, surveying along a rectangular and diagonal network with a step of 25 cm showed different number diffraction hyperbolas. They were markers of separate roots. A pattern of distribution of diffraction hyperbolas in depth was discovered, corresponding to the growth characteristics of the tree under study. To verify the data, a complete excavation of spruce roots was conducted with a detailed manual description. In particular, it has been established that large roots have characteristic GPR patterns that can be traced on a series of parallel profiles. The reflected signal for the roots was analyzed and the relationship between their diameter and the length of the wave train was shown with a correlation coefficient of r = 0.87. Based on a survey of European spruce, GPR data made it possible to restore the root architecture in situ and determine criteria for searching for the largest coarse roots. Although there are problems associated with parameterization of roots, the results got show the possibility of obtaining new information about the structure and functioning of tree root systems.