Fine Resolution Signatures of Coniferous and Deciduous Trees at C Band

A very fine resolution frequency-modulated, continuous-wave (FM-CW) radar scatterometer with a range resolution of 11·5 cm and a footprint 20 cm in diameter at a range of 4·5 m was used to investigate the backscattering and attenuation sources in sugar maple, pin oak and pine trees at incidence angles of 30° and 50° with vertical, horizontal and cross polarizations. Constituent defoliation to isolate the primary backscatter sources indicated that, at vertical and horizontal polarizations, branchlets and stems account for a major portion of the backscatter and attenuation. With cross-polarization the backscatter was very sensitive to the linear features of the branches (i.e. petioles, stems and branchlets) and not the leaves but, at this polarization, the leaves accounted for all of the attenuation. For pine trees, needles dominated the backscatter and accounted for most of the attenuation. Cones also showed significant backscattering. It was shown that the moisture content, size and relative orientation of tree constituents affected the backscatter and attenuation properties.