MODELING P-BAND SAR RETURNS FROM A RED PINE STAND

Bright P-band synthetic aperture radar (SAR) returns from red pine for ests 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 e ffort was to understand the cause of the high P-band returns. The red pine stand under study consisted of mature trees with an average heigh t of 25 ms and diameters at breast height (DBH) of 28-38 cm. Soil mois ture and soil bulk density measurements were made along with ground ro ugh 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. Comp utations indicate that the direct-reflected contributions from the gro und are responsible for the high P-band HH observed returns. Tapered t ree trunks have been used in the model to improve the accuracy of the direct-reflected calculation. The high P-band returns from red pine co ntrast with the results from previous studies of a hemlock forest in t he area, which have lower P-band returns mainly due to backscattering from branches.