A frequency spectrum-based processing framework for the assessment of tree root systems

The monitoring and conservation of natural assets are nowadays increasingly important, as the emergence of unknown pathogens endangers tree survival. In this respect, root systems are affected by fungal infections that cause root rot and ultimately contribute to the death of trees. Such diseases can quickly spread to surrounding trees and affect wider areas. Since these decays do not usually show visible symptoms, early identification is key to the protection of trees. Within this framework, non-destructive testing (NDT) methods are becoming increasingly popular, as they are faster and more flexible than destructive methods. Specifically, ground penetrating radar (GPR) is emerging as an accurate geophysical tool for tree roots mapping. Recent research has focused on the implementation of automated algorithms for root mapping in a 3D environment and the investigation of root mass density. This research aims to investigate the changes occurring in the frequency spectrum of the GPR signal during root system surveys. To this extent, advanced signal processing techniques (both in time and frequency domain) are applied, to eliminate noise-related information and the disturbance induced by the presence of other features (i.e. pavement layers or underground utilities). The proposed processing framework can be applied for expeditious analyses or on trees difficult to access, where more comprehensive survey methods are not applicable. The results of the application of this methodology to a real-case scenario showed the potential of the applied procedure and will lead to the development of a new approach for investigating root systems using GPR.