Tropical forest canopies are the biosphere’s most concentrated atmospheric interface for carbon, water and energy^1,2. However, in most Earth System Models, the diverse and heterogeneous tropical forest biome is represented as a largely uniform ecosystem with either a singular or a small number of fixed canopy ecophysiological properties³. This situation arises, in part, from a lack of understanding about how and why the functional properties of tropical forest canopies vary geographically⁴. Here, by combining field-collected data from more than 1,800 vegetation plots and tree traits with satellite remote-sensing, terrain, climate and soil data, we predict variation across 13 morphological, structural and chemical functional traits of trees, and use this to compute and map the functional diversity of tropical forests. Our findings reveal that the tropical Americas, Africa and Asia tend to occupy different portions of the total functional trait space available across tropical forests. Tropical American forests are predicted to have 40% greater functional richness than tropical African and Asian forests. Meanwhile, African forests have the highest functional divergence—32% and 7% higher than that of tropical American and Asian forests, respectively. An uncertainty analysis highlights priority regions for further data collection, which would refine and improve these maps. Our predictions represent a ground-based and remotely enabled global analysis of how and why the functional traits of tropical forest canopies vary across space.

Tropical forests cover large areas of equatorial Africa and play a substantial role in the global carbon cycle. However, there has been a lack of biometric measurements to understand the forests’ gross and net primary productivity (GPP, NPP) and their allocation. Here we present a detailed field assessment of the carbon budget of multiple forest sites in Africa, by monitoring 14 one-hectare plots along an aridity gradient in Ghana, West Africa. When compared with an equivalent aridity gradient in Amazonia, the studied West African forests generally had higher productivity and lower carbon use efficiency (CUE). The West African aridity gradient consistently shows the highest NPP, CUE, GPP, and autotrophic respiration at a medium-aridity site, Bobiri. Notably, NPP and GPP of the site are the highest yet reported anywhere for intact forests. Widely used data products substantially underestimate productivity when compared to biometric measurements in Amazonia and Africa. Our analysis suggests that the high productivity of the African forests is linked to their large GPP allocation to canopy and semi-deciduous characteristics.

Tropical forests dominate terrestrial photosynthesis, yet there are major contradictions in our understanding due to a lack of field studies, especially outside the tropical Americas. A recent field study indicated that West African forests have among the highest forests gross primary productivity (GPP) yet observed, contradicting models that rank them lower than Amazonian forests. Here, we show possible reasons for this data-model mismatch. We found that biometric GPP measurements are on average 56.3% higher than multiple global GPP products at the study sites. The underestimation of GPP largely disappears when a standard photosynthesis model is informed by local field-measured values of (a) fractional absorbed photosynthetic radiation (fAPAR), and (b) photosynthetic traits. Remote sensing products systematically underestimate fAPAR (33.9% on average at study sites) due to cloud contamination issues. The study highlights the potential widespread underestimation of tropical forests GPP and carbon cycling and hints at the ways forward for model and input data improvement.

The impact of land-use change (LUC) on soil organic carbon (SOC) has been a wide concern of land management policymakers because CO₂ emissions induced by LUC have been the second largest carbon source worldwide. However, due to insufficient data quality and limited biome coverage, a global big picture of the impact of LUC on SOC is still not clear. This study conducted a meta-analysis on 288 independent observations sourced from 62 peer-reviewed papers to provide a global summary of the change in SOC after the conversion of primary forests into other land-use types. The conversion of primary forest to cropland resulted in the most severe SOC loss (−33.2%), followed by conversion into plantation forests (−22.3%) and secondary forests (−19.1%). Nonetheless, SOC increased by 9.1% after a conversion from primary forests into pasture. More SOC loss was found at sites with lower precipitation for primary forests converted to cropland and plantation forests. The SOC loss decreased consistently with increasing mean annual temperature (MAT) for all four types of LUC. Moreover, the loss of SOC tended to worsen over time when primary forests are converted to cropland or plantation forests. In contrast, SOC loss recovered over time following conversion to secondary forests. The gain of SOC gradually increased over time after conversion to pastures. To conclude, the changes in SOC are related not only to the land-use type but also to precipitation, temperature and turn years after LUC. Due to limited data, this study focuses on soil profiles within 30 cm depth, and future research should explore SOC dynamics induced by LUC at greater depths. Overall, cases of SOC loss of approximately 30% following deforestation were very common (except for conversion to pasture), and the results of this study show that the loss of SOC following LUC should be carefully considered and monitored in land management.

The effects of altered fire regimes within open ecosystems are poorly understood and can have serious consequences on functioning and conservation across savanna ecoregions worldwide. In South American savannas like the Cerrado, there is a gap of knowledge relating to carbon cycling in the presence of fire, meaning the impacts of altered fire regimes on the carbon fluxes and budgets are virtually unknown. We thus investigate vegetation carbon flux dynamics within the Cerrado making use of an experimental fire and carbon monitoring research project at the Estação Ecológica da Serra das Araras, Brazil. We present a thorough carbon budget of woodland-type savannas (cerrado sensu stricto), and investigate how annual (every year), biennial (every two years), and triennial (every three years) controlled fire frequencies have influenced net primary productivity and respiration fluxes. Six years of experimental fire had noticeable effects on the vegetation structure and carbon dynamics, reducing woody cover and productivity in favour of grass-dominated carbon balances. Woody NPP increased by 35 % in the unburnt plots from 2017 to 2019 to 2021-2023, but decreased by 75 %, 33 % and 20 % in the triennial, biennial and annual fire frequencies. By 2023, burnt plots revealed around three times higher herbaceous NPP than unburnt plots. Fluxes corresponding to different ecosystem components (canopy, stems, roots, herbs) showed varying patterns of change across the gradient of experimental fire frequencies, indicating other fire regime properties distinctively affect each vegetation segment. Fire intensity and severity appear to be linked with patterns in woody stems and the herbaceous layer. Our results indicate periodically burnt cerrado sensu stricto vegetation experiences different carbon dynamics than unburnt vegetation. Burning is revealed as a strategy that can successfully limit woody encroachment and help conserve open ecosystem structure in the Cerrado. Our study highlights the importance of long-term monitoring efforts in investigating the effects of management interventions and environmental shifts on ecosystem functioning.