Sonic root detector to reveal the distribution of tree coarse roots in soil: a first case study in Italy

The root architecture—the root radial and vertical distribution in the soil—is involved in different plant functional roles, such as nutrient and water acquisition and mechanically active anchorage. Due to the underground growth habitat, tree root architecture has been mainly determined by destructive methods that require root excavation from the soil and the three-dimensional digitizing by different 3D digitizers (FASTRAK®, GTCO Freepoint 3D). However, these root techniques are extremely time consuming, labor intensive, and impratical, especially in urban environments. Fortunately, in the past decade, portable and noninvasive methods to detect and visualize the root system have been used commercially. This communication describes a pilot study to investigate the reliability of a nondestructive method (i.e., the Root-Detector, Fakopp Enterprise Bt) for detection and determining the radial distribution of individual roots of olive trees in the soil, by statistical linear and radial correlations of the sonic speed data with those obtained from the real root horizontal and vertical distribution by 3D digitizer (Fastrak®, Polhemus). Outcomes clearly showed that the Root Detector was able to map the olive roots in the soil environment, but with some conditions. First, the detection of roots by the Root Detector was more efficient within 30 cm of soil depth. Second, at the farthest distance from the trunk (>120 cm), the sonic speed and detection of the roots were reduced. Third, the Root Detector technology fails to detect the root size in terms of geometric parameters such as root diameter.