GEDI-constrained Estimates of Terrestrial Carbon Dynamics in Southeast Asian Tropical Forests over the Coming Century

Global tropical rainforests represent an important carbon sink and have significant potential for mitigating the effects of human-induced climate change. However, current estimates of carbon stocks and fluxes in tropical forests are highly uncertain due to spatial variation in structure, composition, and dynamics of tropical forests. Canopy structure metrics, including vertical leaf area index (LAI) profiles, canopy height and biomass have been identified as essential variables for predicting tropical forest canopy biomass dynamics and climate feedbacks in heterogeneous landscapes. In this study, we assimilate lidar-derived measurements of forest canopy height and vertical LAI profile from NASA’s Global Ecosystem Dynamics Investigation (GEDI), space-borne lidar into ED2, a cohort-based terrestrial biosphere model. We then use the GEDI-constrained model to analyze carbon dynamics across Southeast Asia under different scenarios and climate forcings. In addition, we carried out model simulations without GEDI observations to evaluate how different initialization methods would impact predictions of carbon fluxes and states. Our results show that GEDI constrained model has similar predictions with ground-data initialized simulations. In addition, regional analysis of long-term regional simulations suggests that initialization with GEDI as opposed to with output from a historical simulation has larger effects on regional-scale aboveground biomass predictions than in the effects of future CO₂ emissions, land use scenarios, and climate forcings. Our study demonstrates how information on forest structure from GEDI retrievals can improve the accuracy of TBM predictions of carbon dynamics in tropical forests and thereby inform decisions about how tropical forests can be managed to promote forest carbon storage and uptake in context of ongoing changes in earth’s climate.