Use of Ground-Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) to Study Tree Roots Volume in Pine Forest and Poplar Plantation

The evaluation of tree root biomass is significant and difficult to survey accurately. Traditional approach used for roots biomass harvest (e.g., soil cores and trenches) provide reasonable accurate information but they are destructive in nature, labour intensive, and limited whit respect to soil volume and surface area that can be assessed. Data derived from traditional root extraction approaches are also generally limited to root biomass averages across plots or treatments rather than information on root distribution. Sampling needed to detect difference among treatments can be expensive as well as time consuming for technical personal. For the above reason test and develop new indirect tools for roots biomass survey appears of leading importance. In this study we have assessed the possibility to use Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) as a root volume indirect survey investigation. Although previous studies have demonstrated the potentiality of these methodology to detect root systems (J. R Butnor et al 2001 J. Hruska et al 1999 L. Wielopolski, et al 2000) up to now few research (Stokes et al, 2002; ) has tried to compare the GPR and ERT response with direct observations of the entire root system. The research showed that Geophysical surveys can reveal a useful approach to roots investigation, both in describing the shape and behavior of the roots in the subsoil and in estimating the volumes of root biomass. To achieve the better results this paper underlines the need of integrating different techniques: GPR method is able of detecting with higher resolution the distribution of the tree roots in the subsoil. Three dimensional ERT can be useful in correlating the recovered resistivity distribution with root volumes. In particular the extraction of volumes of resistivity percent increment between dry and wet conditions in the subsoil around the trees seems a parameter that can be directly related to the volumes of roots. Further studies should focus on two directions: first, the improvement of a standard field-procedure to carry on the geophysical surveys; second, the development a statistical processing tool to relate root biomass to geophysical parameters.JRC.H.2-Climate chang