Mapping tropical forest carbon: Calibrating plot estimates to a simple LiDAR metric

Mapping aboveground carbon density (ACD) in tropical forests can enhance large-scale ecological studies and support CO₂ emissions monitoring. Light Detection and Ranging (LiDAR) has proven useful for estimating carbon density patterns outside of field plot inventory networks. However, the accuracy and generality of calibrations between LiDAR-assisted ACD predictions (EACD_LiDAR) and estimated ACD based on field inventory techniques (EACD_field) must be increased in order to make tropical forest carbon mapping more widely available. Using a network of 804 field inventory plots distributed across a wide range of tropical vegetation types, climates and successional states, we present a general conceptual and technical approach for linking tropical forest EACD_field to LiDAR top-of-canopy height (TCH) using regional-scale inputs of basal area and wood density. With this approach, we show that EACD_LiDAR and EACD_field reach nearly 90% agreement at 1-ha resolution for a wide array of tropical vegetation types. We also show that Lorey's Height - a common metric used to calibrate LiDAR measurements to biomass - is severely flawed in open canopy forests that are common to the tropics. Our proposed approach can advance the use of airborne and space-based LiDAR measurements for estimation of tropical forest carbon stocks.