Plant and Soil

, Volume 395, Issue 1–2, pp 289–305 | Cite as

Calibrating the impact of root orientation on root quantification using ground-penetrating radar

  • Li Guo
  • Yuan Wu
  • Jin Chen
  • Yasuhiro Hirano
  • Toko Tanikawa
  • Wentao Li
  • Xihong Cui
Regular Article

Abstract

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.

Methods

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).

Results

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.

Conclusions

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.

Keywords

Coarse root Field plot scale Nondestructive root method Root angle Root diameter Root biomass 

Abbreviations

GPR

Ground-penetrating radar

x

Root angle subtended to the transecting line

A

Amplitude area

A

Sum of the amplitude areas for all reflection waveforms

Single Amax

Amplitude area of the maximum reflection waveform

B

Amplitude area of the soil background

EM

Electromagnetic

RMSE

Root mean square error

Supplementary material

11104_2015_2563_MOESM1_ESM.docx (16 kb)
ESM 1(DOCX 16 kb)

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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Li Guo
    • 1
    • 2
  • Yuan Wu
    • 3
  • Jin Chen
    • 1
    • 2
  • Yasuhiro Hirano
    • 4
  • Toko Tanikawa
    • 5
  • Wentao Li
    • 3
  • Xihong Cui
    • 3
  1. 1.College of Global Change and Earth System ScienceBeijing Normal UniversityBeijingChina
  2. 2.Joint Center for Global Change StudiesBeijingChina
  3. 3.State Key Laboratory of Earth Surface Processes and Resource EcologyBeijing Normal UniversityBeijingChina
  4. 4.Graduate School of Environment StudiesNagoya UniversityNagoyaJapan
  5. 5.Kansai Research Center, Forestry and Forest Products Research InstituteKyotoJapan

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