Carbon accumulation rate peaks at 1,000-m elevation in tropical planted and regrowth forests

Tropical planted and regrowth forests (TPRFs) are one of the most low-cost components for recovering biomass-stored carbon in the tropics. Nevertheless, challenges persist in pinpointing which elevational ranges exhibit the largest carbon accumulation rate ( γ r a p i d ) due to the highly inconsistent previous assessments. This prevents the selection of optimal locations for implementing large-scale reforestation in the tropics. Here, we proposed a refined approach that used a carbon accumulation threshold (<80% of the maximum value) to quantify γ r a p i d in TPRFs at various elevations. We find that γ r a p i d increases with elevations from 300 to 1,000 m and declines at elevations >1,000 m. TPRFs at elevations ∼1,000 m exhibit three times more γ r a p i d than lowland TPRFs. This optimal elevation, highly dependent on background temperatures, varies slightly but significantly across different mountains. These findings provide guidelines for policymakers to determine the optimal elevations from regional to continental scales when implementing reforestation initiatives in the tropics.