Long-term decline in above-ground carbon sinks in Brazilian tropical and subtropical forests.

Recent evidence indicates that Brazilian forests are shifting from persistent carbon sinks to emerging carbon sources, with important implications for the global climate. To investigate this trend, we analyse long-term census data from 49 forest sites spanning southeast and southern Brazil, including tropical and subtropical forests. We examine above-ground carbon dynamics and its relationship with tree diversity and functional traits that are tightly linked with species' carbon processing and storage capacities. Our findings reveal a long-term trend of taxonomic, functional and phylogenetic homogenisation and a decline in the forests' above-ground carbon sink. Specifically, homogeneous forests have lower carbon losses, whilst forests with more conservative species are associated with greater carbon gains and lower carbon losses. Overall, our study establishes a baseline to understand and predict the above-ground carbon sink in the face of ongoing climate change in this region.