Detection of buried tree root samples by using geoelectrical measurements: a laboratory experiment

The aim of this study was to test the possibility of using geoelectrical measurements to detect and differentiate different root samples of trees rooted in dikes. A laboratory experiment was performed to describe the electrical signal of buried freshly cut root samples according to tree species, root sample orientation and number and nature of earthfill materials. The geoelectrical measurements were performed at the soil surface in containers. First, the electrical properties of three soil materials (gravel, sand and silt) were characterized in containers without buried roots. In subsequent steps, the root samples were buried at a depth of 0.05 m with different orientations: horizontally and parallel or perpendicular to the electrode array, and vertically. The complex conductivity spectra were observed in the frequency range 22.9 mHz-750 Hz. The measurements without buried roots were repeated after completing all the measurements with the roots. In most cases, the conductivity of buried root samples increased the integral conductivity of the ground. This trend was observed mainly in gravel and sand. The parallel orientation resulted in the most significant increase of the real part of conductivity. Channelling of the current flow in the root seems to be a reliable explanation. This laboratory experiment now opens the way for in-situ measurement.