Reconstruction of forest litter horizons using ground-penetrating radar

Forest litter constitutes a major component of forest ecosystems and its detailed characterization is necessary for thorough understanding and modeling of ecosystem functioning. Besides, the presence of litter is acknowledged to influence remote sensing radar data over forested areas and their proper processing requires accurate quantification of litter properties. In this work, ultra wideband (0.8-2.2 GHz) ground-penetrating radar (GPR) data were collected in situ for contrasted litter types to examine the ability of the technique to reconstruct litter constitutive properties. GPR data were processed resorting to full-wave inversion. Good agreement was generally observed between measured and estimated litter layer thicknesses. Yet, no significant correlation was found between both sets of values for recently fallen litter (OL layer) as a result of relatively large estimation and measurement errors compared with the limited variation range of this parameter. Furthermore, discrepancies between litter thickness estimates and measurements were also partly ascribed to weak dielectric contrasts both amongst litter layers and between litter and the organo-mineral A horizon. Reliable estimates of litter electromagnetic properties were also obtained from radar signal inversions. These results show promising potentialities of GPR for non-invasive characterization and mapping of forest litter.