Abstract
Accurate characterization of forest litter is of high interest for land surface modeling and for interpreting remote sensing observations over forested areas. Due to the large spatial heterogeneity of forest litter, scattering from litter layers has to be considered when sensed using microwave techniques. Here, we apply a full-waveform radar model combined with a surface roughness model to ultrawideband ground-penetrating radar (GPR) data acquired above forest litter during controlled and in situ experiments. For both experiments, the proposed modeling approach successfully described the radar data, with improvements compared to a previous study in which roughness was not directly accounted for. Inversion of the GPR data also provided reliable estimates of the relative dielectric permittivity of the recently fallen litter (OL layer) and of the fragmented litter in partial decomposition (OF layer) with, respectively, averaged values of 1.35 and 3.8 for the controlled experiment and of 3.9 and 7.5 for the in situ experiment. These results show the promising potentialities of GPR for efficient and non-invasive characterization of forest organic layers.
Highlights
Accurate soil surface characterization is essential for the understanding and the modeling of the various processes occurring at the soil-vegetation-atmosphere interface
Full-wave inversion of the ground-penetrating radar (GPR) signal was used to evaluate the applicability of the proposed radar model accounting for surface roughness to forest litter characterization
A full-waveform radar modeling approach combined with the Ament roughness model was applied to radar data collected above litter in order to investigate its ability to provide quantitative characterization of forest floor organic layers in terms of their surface roughness and their constitutive properties
Summary
Accurate soil surface characterization is essential for the understanding and the modeling of the various processes occurring at the soil-vegetation-atmosphere interface. Given its ability to provide efficient and non-invasive characterization of soil and materials, ground penetrating radar (GPR) appears as being a convenient tool to characterize litter layers with fine spatial and/or temporal resolutions over relatively large areas. This geophysical technique could be used to both study the effects of litter on the microwave signal from proximal measurements and determine litter constitutive properties. The results of the present approach including a physical description of scattering through a roughness model are compared with those obtained previously by considering frequency dependence of effective electrical conductivity of litter to account for scattering together with dielectric losses
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