A ground penetrating radar (GPR) and root excavation study were conducted to determine the efficacy of GPR for estimating subsurface tree root volume. The survey was conducted in sandy soil, which is favorable for GPR imaging. The tree was a loblolly pine (Pinus taeda) that was isolated from other trees to minimize outside influences. GPR antenna frequencies of 450 MHz, 900 MHz, and 1200 MHz were used to map subsurface profiles over a 9-m2 sample grid, and six 1-m2 cells of the root system were subsequently excavated to a depth of 1 m for verification. The 900 MHz GPR was successful at mapping the larger tree roots (>2 cm) and some smaller roots (<2 cm). A simple approach based on average signal strength was used to estimate root volume from the GPR data. The total root volume estimate based on the GPR data compared well with the total root volume determined from the in situ measurements when information from all of the excavated cells was used (<2% error). However, accuracy reduced significantly (30% error) when only three verification cells were used, representing near, intermediate, and far distances from the tree. Matching the GPR root volume to a particular in situ root volume did not improve the root volume estimation.

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