Use of ground penetrating radar for assessing interconnections between root systems of different matured tree species

This study presents recent advances achieved in the use of ground penetrating radar (GPR) for the health monitoring of tree root systems. The main objectives of the research were to provide an effective and high-resolution mapping of the root systems belonging to different species of matured trees, as well as to investigate areas of roots interconnection. To this purpose, a data processing methodology based on three main stages was developed. A pre-processing algorithm was first proposed to remove noise-related information from the raw data and to enhance deep reflections from attenuated targets. Afterwards, an algorithm for identification of targets (i.e. the vertices of the reflection hyperbolas) and their automated tracking in a three-dimensional environment was developed. A third stage was focused on estimating tree root density with emphasis on the interconnection area. To test the feasibility of the proposed methodology, the soil around two different tree species (i.e. maple and ash trees) was investigated using a ground-coupled GPR system equipped with a 700 MHz central frequency antenna. The method has proven to identify distinctive features of both trees, in terms of shallow (i.e. within the first 25 cm from the soil surface) and deep (i.e. deeper than 25 cm from the soil surface) root systems. In addition, results have allowed to assess how different root systems interact with each other.