|Tree Biomass Estimation from Airborne Radar Data|
Tropical savannas cover approximately 15% of the Earth's land surface, constitute the 3rd largest global stock of carbon after tropical and temperate forests, and are highly productive ecosystems with a net primary productivity that is second only to tropical forests. Undisturbed tropical savannas contribute to global tropical biodiversity, containing a rich diversity of tree, shrub and herbaceous plants. Yet due to lack of protection, savannas are often under more stress from land use change than tropical forests. They are therefore prime candidates for monitoring by remote sensing, yet have received little attention from the remote sensing community.
This study will evaluate the capability of Synthetic Aperture Radar (SAR) for estimating the canopy height and above-ground biomass of the tropical savanna woodlands of a well-studied test site in Belize. The test site lies within the Rio Bravo Conservation & Management Area (RBCMA) of NW Belize, 100,000ha of remnant rainforest and semi-natural savanna areas forming the largest privately protected area in Belize. The specific site chosen is a tract of savanna extending over some 70 km2 to the south-east of Hillbank research centre (17° 36N, 88° 39W) where our staff have conducted vegetation surveys since 1996. It is chosen for its range of savanna vegetation types occurring in a limited area of low-lying, gradually varying relief, the recent completion of a detailed botanical inventory and land cover classification for this savanna area, the high quality and currency of ground control points (GCP) available and the accessibility to the site from the Hillbank.
There is a widespread assumption that the relationships between radar intensity and biomass observed over temperate forests will translate directly to savanna woodland, despite important differences in growth patterns and structural composition. The focus of this study is to evaluate the extent to which this assumption holds true, using both long wavelength radar intensity measurements and interferometric height as biomass indicators.