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Region-specific forest structure pathways reveal climate effects on old-growth tropical forest biomass
Covering 45% of Earth’s forested area, tropical forests store a large amount of carbon equivalent to about one-third of the carbon present in the atmosphere, with old-growth forests holding a large amount of it in their aboveground biomass (AGB)1,2,3,4,5,6. Moreover, they host over 50% of terrestrial species, with unparalleled biodiversity and endemism7,8,9,10,11. Preserving these carbon-rich and ecologically vital ecosystems is imperative, as they are heavily threatened by deforestation, forest degradation, defaunation, and climate change12,13. Despite their well-recognized role in the global carbon budget, tropical forests remain the most uncertain component1. A major challenge in mapping and predicting tropical forest carbon stocks globally lies in our limited understanding of how abiotic factors influence the spatial distribution of AGB. Old-growth tropical forests, approaching structural equilibrium with their local environment, are well suited for investigating this question14. Yet, across studies that have explored spatial relationships between plot-level AGB in old-growth forests and environmental factors such as temperature, precipitation, topography, and soil properties, results vary widely in both magnitude and direction. For instance, it is not clear whether increases in annual precipitation are systematically associated with increases in biomass: some studies report a positive relationship in African and Southeast Asian forests15,16, whereas others in...
