Estimation of the Weight of Vegetation Using Microwave Transmission Measurements

This work reports on a technique for inferring the weight of standing vegetation from microwave transmission measurements. This nondestructive technique is invaluable when it is necessary to remeasure vegetation plots to examine effects with time. Such applications include ecological studies of the forest understory. Results are reported for field tests with pine trees in Virginia and stands of softwood, hardwood, and mixed-wood in Maine. It was found that depolarization-compensated attenuation at 12 GHz is highly correlated with the weight of vegetation and woody shoots less than 1.27 cm (one-half inch) in diameter along the signal path. The method was applied to ecological studies into ways of reducing spruce budworm defoliation.