Belowground Analysis of Tree Root Systems Under Temperate Tree-Based Inter-Cropping with the Use of Ground Penetrating Radar.

Understanding tree root structure and function is critical in an agroforestry system, but destructive sampling is typically required. Geoimages of the subsurface generated with the use of ground penetrating radar (GPR) provide a means to assess belowground root systems more efficiently and less destructively.

Subsurface data are being collected surrounding five temperate tree species at the University of Guelph Agroforestry Research Station in southern Ontario, Canada using a 1GHz GPR system. The on-going research is focused on depicting tree root distribution 3-dimensionally. Mapped tree root systems will then be combined with data on fine root densities and diameter-dependent root carbon content to provide insight into belowground competition and carbon storage within an inter-cropping system.

In order to determine accuracy, geoimaged root reflection patterns are being compared to distribution of coarse roots sampled during full-tree excavation. Preliminary GPR data collection at the study site illustrate that site soil conditions are suitable for GPR image analysis and that detected location and depth of coarse tree roots is accurate to diameters as small as 0.5 cm.

It is anticipated there will be species variance of root distribution and root carbon content, thus having consequences for both tree-crop competition and belowground carbon storage in this tree-based inter-cropping system. These novel techniques could have far reaching implications for other treed environments, both natural and managed, including increasing precision in belowground biomass estimation and improving carbon sequestration calculations.