Estimation of tropical forest aboveground biomass using large-footprint lidar (Costa Rica)

Accurate estimates of aboveground biomass provide critical information for modeling carbon dynamics in terrestrial ecosystems. Although aboveground biomass is difficult to quantify over large areas using traditional techniques, large-footprint lidar remote sensing holds great promise for biomass estimation because vertical forest structure is directly sampled. Large-footprint lidar remote sensing techniques have proven successful in accurately estimating forest structural characteristics such as biomass in a variety of temperate forests, however they remained untested in dense, closed-canopy tropical forest ecosystems that contain a large portion of the carbon found in terrestrial vegetation globally.; The first stage of this research developed relationships between metrics from an airborne scanning lidar instrument and forest structural characteristics in a tropical rainforest in Costa Rica. Lidar metrics were strongly correlated with aboveground biomass, basal area and mean stem diameter through a successional spectrum of conditions sampled from recently abandoned pasture to primary tropical forest.; The second stage of this research explored the sensitivity of lidar to differences in canopy structure and aboveground biomass at Costa Rican rainforest. Vertical canopy profiles were developed from field measurements as a basis of comparison with lidar-derived profiles. Metrics from field profiles were highly correlated with both aboveground biomass and corresponding lidar profile metrics. As a result, lidar profile metrics were also highly correlated with aboveground biomass through the entire range of conditions sampled in this Neotropical landscape.; The final stage examined the generality of relationships between lidar metrics and aboveground biomass at two study areas in Central America with different average annual precipitation levels. Lidar metrics were strong predictors of basal area and mean stem diameter at both study areas, however the relationships were significantly different at the two study areas until the deciduousness of canopy trees in Panama was considered. Lidar metrics and aboveground biomass were also strongly correlated, however, relationships remained significantly different between the two study areas primarily due to the different general allometric relationships used to estimate aboveground biomass in tropical wet forests and tropical moist forests. Together these results demonstrate that lidar remote sensing should greatly aid efforts to quantify aboveground biomass in terrestrial vegetation globally.