Microwave Remote Sensing for Monitoring Forest Vitality.

The physiological activity of a forest stand is influenced by the vitality and health status of the trees. Our studies aim on investigating the capability of microwaves for monitoring forest vitality. Reduced forest tree vitality and reduced canopy biomass are often a consequence of disadvantageous stand conditions like lack of water supply and low nutrient availability in the soil. Pollutants in the air and the soil can negatively affect the metabolism of the trees and cause visible decline symptoms. Reduced vitality ultimately leads to a decreasing leaf or needle biomass and thus canopy density. We further assume that a direct relationship exists between the variations of the tree water status and the canopy density, stand vitality and forest decline. Since the dielectric constant of water is much higher than of other tree constituents, microwave signatures contain direct information on the water status of forest canopies. This experiment comprises three major parts: detailed ground truth collection, backscatter modeling and comparative and synergistic analysis of data from ERS-1/2 and DLR's airborne E-SAR in order to derive optimum frequency/polarization combinations to retrieve stand vitality parameters.