Application of Ground Penetrating Radar to Quantify the Effects of Long-term CO2 Enrichment on Coarse Root Biomass in a Scrub-Oak Ecosystem at Kennedy Space Center, Florida USA.
Daniel B. Stover1, Frank P. Day1, John R. Butnor2, and Bert G. Drake3. (1) Old Dominion Univ, Dept of Biological Sciences, Norfolk, VA 23529, (2) US Forest Service, Southern Research Station, Research Triangle, NC 27709, (3) Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, MD 21037
The growth and distribution of coarse roots in time and space represent a gap in our understanding of belowground ecology. Large roots may play a critical role in the sequestration of carbon belowground. We used ground-penetrating radar (GPR) to quantify coarse root biomass in an open-top chamber experiment in a scrub-oak ecosystem at Kennedy Space Center, Florida USA. Plant communities within the chambers have been exposed to elevated atmospheric CO2 for nine years. GPR propagates electromagnetic waves (~100-1,500 MHz) directly into the soil, and when a buried object is contacted, a portion of the energy is reflected back to the receiving unit. The advantages of this non-destructive method include rapid acquisition of belowground data. In our study, we utilized a 1,500 MHz antenna to establish correlations between GPR signals and root biomass. A significant relationship was found between GPR signal reflectance and biomass (R2 = 0.7103). This correlation was applied to five GPR scans taken from each open-top chamber (elevated and ambient CO2 conditions). Our results showed that plots receiving elevated CO2 had significantly greater coarse root biomass (8,059.79 ± 833.03 g m-2 to a depth of 60 cm) compared to ambient plots (5,740.20 ± 544.26 g m-2). These results indicated a significant (p = 0.022) CO2 treatment effect within the coarse root component of the scrub-oak ecosystem. This suggests that coarse roots may play a large role in the sequestration of carbon in the scrub-oak ecosystem. Although still in its infancy, this method holds much promise for rapid and repeatable identification and quantification of coarse roots, which are currently the most elusive aspect of the long-term study of root systems.