Estimating forest biomass using satellite radar:: an exploratory study in a temperate Australian Eucalyptus forest

A study was undertaken to explore the relationship between backscattering coefficients from a Japanese Earth Resources Satellite synthetic aperture radar (JERS-1 SAR) image and aboveground biomass sampled at 12 field plots located in Murramarang National Park, New South Wales, Australia. This is the first such investigation in Australian Eucalyptus forests. From the field survey we obtained tree and coarse woody debris (CWD) measurements for eight forested, two paddock tree and two grass (effectively zero biomass) plots. Total aboveground and component biomass were estimated for all plots using allometric equations. Live aboveground woody biomass ranged from 0 to 610 t ha(-1). The mean JERS-1 SAR backscattering coefficients for the field plot areas ranged from -12.4 to -7.0 dB. The results show positive linear trends between backscattering coefficients and the biomass components of dry Eucalyptus forest. The strongest trend was produced with small branch (2 cm) biomass estimates (r(2) = 0.84). The biomass saturation level for the JERS-1 SAR data may be higher than estimated by other studies (possibly up to 600 t ha(-1)), although this trend was not statistically confirmed due to the small sample size (n = 8). The results suggest that estimation of forest biomass for biomass inventories in Australia might be possible using satellite radar data when landscape characteristics such as topography, surface water, and forest structure are taken into account. (C) 2002 Elsevier Science B.V. All rights reserved.