Quantitative, nondestructive estimates of coarse root biomass in a temperate pine forest using 3‐D ground‐penetrating radar (GPR)

Abstract

Coarse root biomass was estimated in a temperate pine forest using high‐resolution (1 GHz) 3‐D ground‐penetrating radar (GPR). GPR survey grids were acquired across a 400 m2 area with varying line spacing (12.5 and 25 cm). Root volume and biomass were estimated directly from the 3‐D radar volume by using isometric surfaces calculated with the marching cubes algorithm. Empirical relations between GPR reflection amplitude and root diameter were determined for 14 root segments (0.1–10 cm diameter) reburied in a 6 m2 experimental test plot and surveyed at 5–25 cm line spacing under dry and wet soil conditions. Reburied roots >1.4 cm diameter were detectable as continuous root structures with 5 cm line separation. Reflection amplitudes were strongly controlled by soil moisture and decreased by ~40% with a twofold increase in soil moisture. GPR line intervals of 12.5 and 25 cm produced discontinuous mapping of roots, and GPR coarse root biomass estimates (0.92 kgC m−2) were lower than those obtained previously with a site‐specific allometric equation due to nondetection of vertical roots and roots <1.5 cm diameter. The results show that coarse root volume and biomass can be estimated directly from interpolated 3‐D GPR volumes by using a marching cubes approach, but mapping of roots as continuous structures requires high inline sampling and line density (<5 cm). The results demonstrate that 3‐D GPR is viable approach for estimating belowground carbon and for mapping tree root architecture. This methodology can be applied more broadly in other disciplines (e.g., archaeology and civil engineering) for imaging buried structures.

Pairing dual‐frequency GPR in summer and winter enhances the detection and mapping of coarse roots in the semi‐arid shrubland in China

“…So far, GPR has been tested for visualizing the branching patterns of coarse roots (Guo et al, ; Zhu, Huang, Su, & Sato, ), reconstructing root system architecture and root profiles (Borden, Thomas, & Isaac, ; Raz‐Yaseef, Koteen, & Baldocchi, ; Wu et al, ), quantifying root biomass (Butnor et al, ; Liu et al, ; Molon, Boyce, & Arain, ) and measuring root zone soil moisture (Liu et al, ). Despite the potential of GPR in root investigation, its successful application, however, highly depends on site‐specific conditions and the selection of appropriate GPR systems (Butnor et al, ; Guo, Chen, et al, ).…”

Evaluation of a Ground Penetrating Radar to Map the Root Architecture of HLB-Infected Citrus Trees

“…However, these techniques are expensive and not suited for the large-scale field study of root system differences. A more environmentally friendly, rapid, low-cost, and effective technology for detecting tree roots is ground-penetrating radar (GPR) [21][22][23]. GPR is a technology that is used to detect various subterranean objects through radar pulsations [23].…”

“…A more environmentally friendly, rapid, low-cost, and effective technology for detecting tree roots is ground-penetrating radar (GPR) [21][22][23]. GPR is a technology that is used to detect various subterranean objects through radar pulsations [23]. It operates by mostly transmitting polarized high-frequency radio waves (UHF and VHF) into the ground.…”

“…It operates by mostly transmitting polarized high-frequency radio waves (UHF and VHF) into the ground. Subterranean objects with different dielectric constants are hit with the radio waves and they reflect different signals that can be detected with a receiving antenna [8].The GPR can be used to map tree roots, because it is relatively easy to use in the field and it is non-destructive to trees, roots, and the root-soil environment [21][22][23]. Numerous tree root scans can be performed and replicated in a short time without interfering with root growth.…”

“…The GPR can be used to map tree roots, because it is relatively easy to use in the field and it is non-destructive to trees, roots, and the root-soil environment [21][22][23]. Numerous tree root scans can be performed and replicated in a short time without interfering with root growth.…”