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To achieve more accurate Earth system model projections of diverse climate scenarios, researchers need observation-based data on the movement of carbon between reservoirs, and especially across tropical regions. The Tropical Low-Pressure Belt (TLPB) is a key driver of atmospheric circulation across lower latitudes. While the TLPB shifts across the east–west extent of northern Africa, the extent to which 14C concentrations apply to Afrotropical forests remains untested, restricting our understanding about other carbon feedbacks. Here, we present a high-precision atmospheric 14C record (1940–2012) from a lowland tropical tree species (Entandrophragma utile) in Cameroon. We included 107 measurements from whole rings and 15 intra-annual slices. The intra-annual 14C data from 1962, 1963, and 1964 confirm a 7-month long growing season (April–November) with a photosynthetic profile typical of Northern Hemisphere (NH) sites, and showing no nonstructural-carbohydrate interference. The full 14C record reveals that air masses reaching the site were derived primarily from Southern Hemisphere (SH) readings followed by recycled bomb-14C signals from soil and litter. Radiocarbon results were substantiated by HYSPLIT model trajectories coupled with NCEP/NCAR reanalysis data. The paradox of finding that tropical NH trees grow using 14CO2 of SH air masses and land-surface respiration challenges existing zonal 14C classifications. Our findings highlight an essential role for robust observational 14C data in refining atmospheric models and improving carbon-cycle assessments across distinct climate zones. 

To achieve more accurate Earth system model projections of diverse climate scenarios, researchers need observation-based data on the movement of carbon between reservoirs, and especially across tropical regions. The Tropical Low-Pressure Belt (TLPB) is a key driver of atmospheric circulation across lower latitudes. While the TLPB shifts across the east–west extent of northern Africa, the extent to which 14C concentrations apply to Afrotropical forests remains untested, restricting our understanding about other carbon feedbacks. Here, we present a high-precision atmospheric 14C record (1940–2012) from a lowland tropical tree species (Entandrophragma utile) in Cameroon. We included 107 measurements from whole rings and 15 intra-annual slices. The intra-annual 14C data from 1962, 1963, and 1964 confirm a 7-month long growing season (April–November) with a photosynthetic profile typical of Northern Hemisphere (NH) sites, and showing no nonstructural-carbohydrate interference. The full 14C record reveals that air masses reaching the site were derived primarily from Southern Hemisphere (SH) readings followed by recycled bomb-14C signals from soil and litter. Radiocarbon results were substantiated by HYSPLIT model trajectories coupled with NCEP/NCAR reanalysis data. The paradox of finding that tropical NH trees grow using 14CO2 of SH air masses and land-surface respiration challenges existing zonal 14C classifications. Our findings highlight an essential role for robust observational 14C data in refining atmospheric models and improving carbon-cycle assessments across distinct climate zones. 

Tree growth and longevity trade-offs fundamentally shape the terrestrial carbon balance. Yet, we lack a unified understanding of how such trade-offs vary across the world’s forests. By mapping life history traits for a wide range of species across the Americas, we reveal considerable variation in life expectancies from 10 centimeters in diameter (ranging from 1.3 to 3195 years) and show that the pace of life for trees can be accurately classified into four demographic functional types. We found emergent patterns in the strength of trade-offs between growth and longevity across a temperature gradient. Furthermore, we show that the diversity of life history traits varies predictably across forest biomes, giving rise to a positive relationship between trait diversity and productivity. Our pan-latitudinal assessment provides new insights into the demographic mechanisms that govern the carbon turnover rate across forest biomes. 

Increasing drought pressure under anthropogenic climate change may jeopardize the potential of tropical forests to capture carbon in woody biomass and act as a long-term carbon dioxide sink. To evaluate this risk, we assessed drought impacts in 483 tree-ring chronologies from across the tropics and found an overall modest stem growth decline (2.5% with a 95% confidence interval of 2.2 to 2.7%) during the 10% driest years since 1930. Stem growth declines exceeded 10% in 25% of cases and were larger at hotter and drier sites and for gymnosperms compared with angiosperms. Growth declines generally did not outlast drought years and were partially mitigated by growth stimulation in wet years. Thus, pantropical forest carbon sequestration through stem growth has hitherto shown drought resilience that may, however, diminish under future climate change.