Estimation of Tropical Forest Aboveground Biomass Using Large-footprint Lidar

An essential step in understanding the level to which human activity may contribute to climate change is the clarification of pools and fluxes of carbon in the global carbon cycle.  Although the terrestrial carbon pool represents only a fraction of the oceanic carbon pool, the annual flow between the atmosphere and the terrestrial surface is on the same order as the ocean-atmosphere flow.  As a result, the accurate quantification of terrestrial carbon pools is a critical step in this endeavor.  Because dry above-ground  biomass is about half carbon, it serves as a good predictor of the amount of carbon in terrestrial pools.  However, above-ground biomass has proven difficult to quantify over large areas using ground-based or conventional remote sensing techniques.

Next generation large-footprint Lidar instruments should greatly improve our ability to estimate biomass through measurement of vertical canopy structure.  As part of a pre-launch validation plan for the Vegetation Canopy Lidar (VCL) satellite, in March 1998 the Laser Vegetation Imaging Sensor (LVIS), a large-footprint airborne scanning Lidar, was flown over the La Selva Biological Station in Costa Rica, and Barro Colorado Island (BCI) in Panama. A major objective of this research is to test the ability of large footprint Lidars, such as VCL, to measure vertical canopy structure in dense tropical rainforests for modeling of above-ground biomass.  Above-ground biomass estimates are derived from Lidar-based data and compared to estimates form ground data across a successional spectrum of sites ranging from pasture to primary tropical rainforest.  These techniques are then to be applied to all of the LVIS data over La Selva and BCI, allowing for analysis of landscape-scale spatial patterns of above-ground biomass in two dense tropical forests.  In addition, VCL transects will be simulated over both La Selva and BCI from the existing LVIS data.  Relationships between estimates from this new Lidar instrument and those from ground-based data should indicate how effective this new technology will be for global biomass sampling as a part of the VCL mission.