PNNL

Abstract

Science for society Tropical forests, accounting for approximately 40%–50% of global forest carbon sink, are under threat from ongoing deforestation. Thus, it is essential to regenerate tree cover pan-tropically, either in areas where forests have historically existed or where they have never existed before. Nevertheless, challenges persist in pinpointing which elevational ranges exhibit rapid growth rate. Using multiple data streams, as well as modeling and mapping approaches, our analysis reveals a robust and consistently increasing trend in the tree growth rate at elevations between 300 and 1,000 m but a subsequently declining trend at elevations >1,000 m. This optimal elevation also varies across mountains with different background temperatures. Our findings underscore the importance of elevation impacts on tree growth and can help guide policymakers in implementing reforestation initiatives at optimal elevations in the tropics. Summary 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 (_) 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 (1,000 m. TPRFs at elevations ~1,000 m exhibit three times more 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.