Calibrating the impact of root orientation on root quantification using ground-penetrating radar
Background and aims
Ground-penetrating radar (GPR) has provided a non-invasive means for field root investigation. However, the horizontal cross angle (x) of root orientation intersecting a survey line considerably impacts the amplitude area (A) reflected from a root and impairs the accuracy of GPR-based root quantification. Prediction of A(90°) (the value of A scanning at x = 90°) from multiple A(x) measurements could correct such impact. Previous method of A(90°) prediction focused on target roots at field point scale. The aim of this study is to develop a method to predict A(90°) at field plot scale.
A(90°) was predicted by a pair of A(x) measured at two arbitrary scanning lines together with an estimated soil background amplitude area. Three independent datasets were employed to test the proposed method. The field experiment included radar data collected for six roots of Caragana microphylla in a sandy-clay soil at four cross angles (30°, 45°, 60°, and 90°). The sand box experiment included radar data for 12 dowels at 13 cross angles (0° to 180°, in 15° steps). The simulation experiment included A(x) of 46 simulated roots at 13 cross angles (0° to 180°, in 15° steps).
For all experiments, A(90°) was accurately estimated. Root orientation could also be determined. After correcting the impact of cross angle, the accuracy of root diameter estimation improved. Correlation coefficient between actual and estimated root diameters increased from 0.77 to 0.81, with RMSE declining from 9.53 to 7.05 mm.
A method of correcting the influence of root orientation on root GPR signal at the field plot scale has been established. This method enhances root quantification using GPR.
KeywordsCoarse root Field plot scale Nondestructive root method Root angle Root diameter Root biomass
Root angle subtended to the transecting line
Sum of the amplitude areas for all reflection waveforms
- Single Amax
Amplitude area of the maximum reflection waveform
Amplitude area of the soil background
Root mean square error
- Bassuk N, Grabosky J, Mucciardi A, Raffel G (2011) Ground-penetrating radar accurately locates tree roots in two soil media under pavement. Arboric Urban For 37:160–166Google Scholar
- Butnor JR, Barton CVM, Day FP, Johnsen KH, Mucciardi AN, Schroeder R, Stover DB (2011) Using ground-penetrating radar to detect tree roots and estimate biomass. In: Mancuso S (ed) Measuring roots, an updated approach. Springer, Berlin, pp 213–245Google Scholar
- Hruška J, Čermák J, Sustek S (1999) Mapping tree root systems with ground-penetrating radar. Tree Physiol 19:125–130Google Scholar
- Jol H (2009) Ground penetrating radar, theory and applications. Elsevier, AmsterdamGoogle Scholar
- Stokes A, Fourcaud T, Hruška J, Čermák J, Nadezhdina N, Nadyezhdin V, Praus L (2002) An evaluation of different methods to investigate root system architecture of urban trees in situ: 1. Ground-penetrating radar. J Arboriculture 28:2–10Google Scholar
- Waisel Y, Eshel A, Kafkafi U (2002) Pland roots: the hidden half, 3rd edn. Marcel Dekker, New YorkGoogle Scholar
- Zenone T, Morelli G, Teobaldelli M, Fischanger F, Matteucci M, Sordini M, Armani A, Ferrè C, Chiti T, Seufert G (2008) Preliminary use of ground-penetrating radar and electrical resistivity tomography to study tree roots in pine forests and poplar plantations. Funct Plant Biol 35:1047–1058. doi:10.1071/FP08062 CrossRefGoogle Scholar