MODELING P-BAND SAR RETURNS FROM A RED PINE STAND

Bright P-band synthetic aperture radar (SAR) returns from red pine forests were observed on SAR images taken in the area of Bangor, Maine. A plot of red pine trees in the University of Maine research forest was selected for the characterization and modeling. The purpose of this effort was to understand the cause of the high P-band returns. The red pine stand under study consisted of mature trees with an average height of 25 ms and diameters at breast height (DBH) of 28-38 cm. Soil moisture and soil bulk density measurements were made along with ground rough surface profiles. A tree was cut down in such a manner to keep its crown completely intact. Detailed biomass measurements of the needles, branches and trunks were also made. These site statistics have been used in a distorted Born approximation model of the forest stand. Computations indicate that the direct-reflected contributions from the ground are responsible for the high P-band HH observed returns. Tapered tree trunks have been used in the model to improve the accuracy of the direct-reflected calculation. The high P-band returns from red pine contrast with the results from previous studies of a hemlock forest in the area, which have lower P-band returns mainly due to backscattering from branches.