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Remote Sens. 2017, 9(12), 1337; https://doi.org/10.3390/rs9121337

Experimental Evaluation of Several Key Factors Affecting Root Biomass Estimation by 1500 MHz Ground-Penetrating Radar

1
Department of Biological Sciences, Old Dominion University, Norfolk, VA 23529, USA
2
Southern Research Station, USDA Forest Service, Burlington, VT 05405, USA
*
Author to whom correspondence should be addressed.
Received: 3 November 2017 / Revised: 11 December 2017 / Accepted: 17 December 2017 / Published: 20 December 2017
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Abstract

Accurate quantification of coarse roots without disturbance represents a gap in our understanding of belowground ecology. Ground penetrating radar (GPR) has shown significant promise for coarse root detection and measurement, however root orientation relative to scanning transect direction, the difficulty identifying dead root mass, and the effects of root shadowing are all key factors affecting biomass estimation that require additional research. Specifically, many aspects of GPR applicability for coarse root measurement have not been tested with a full range of antenna frequencies. We tested the effects of multiple scanning directions, root crossover, and root versus soil moisture content in a sand-hill mixed oak community using a 1500 MHz antenna, which provides higher resolution than the oft used 900 MHz antenna. Combining four scanning directions produced a significant relationship between GPR signal reflectance and coarse root biomass (R2 = 0.75) (p < 0.01) and reduced variability encountered when fewer scanning directions were used. Additionally, significantly fewer roots were correctly identified when their moisture content was allowed to equalize with the surrounding soil (p < 0.01), providing evidence to support assertions that GPR cannot reliably identify dead root mass. The 1500 MHz antenna was able to identify roots in close proximity of each other as well as roots shadowed beneath shallower roots, providing higher precision than a 900 MHz antenna. As expected, using a 1500 MHz antenna eliminates some of the deficiency in precision observed in studies that utilized lower frequency antennas. View Full-Text
Keywords: coarse roots; ground penetrating radar; root biomass; 1500 MHz antenna coarse roots; ground penetrating radar; root biomass; 1500 MHz antenna
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Bain, J.C.; Day, F.P.; Butnor, J.R. Experimental Evaluation of Several Key Factors Affecting Root Biomass Estimation by 1500 MHz Ground-Penetrating Radar. Remote Sens. 2017, 9, 1337.

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