Seminar: Eliane Gomes-Alves

Biogenic volatile isoprenoids (isoprene, monoterpenes and sesquiterpenes) are mostly emitted by plants and play key roles ranging from plant defense and chemical signaling to large-scale biogeochemical processes. Amazonia is the largest global source of these compounds, but ongoing land-use and climate changes—especially in the Amazon Arc of Deforestation—may be altering these emissions and subsequent large-scale processes in poorly understood ways. This study identified and quantified isoprenoids from trees and crops in southeastern Amazonia, measuring leaf-level emissions from cotton, corn, and dominant tree species, alongside above-canopy concentrations across a mosaic of forest fragments and agricultural fields. Results showed that monoterpene and sesquiterpene emissions exceeded isoprene emissions for most plant species. Across a degradation gradient, these emissions were up to three times higher in the most disturbed forest areas. Temperature response experiments revealed that at 45°C, plants released up to 35%, 5%, and 23% of recently assimilated carbon as isoprene, monoterpenes, and sesquiterpenes, respectively, indicating significant carbon loss under heat stress. In contrast, ambient air measurements showed lower monoterpene and sesquiterpene concentrations than isoprene, suggesting rapid atmospheric reactivity and that leaf-level observations are needed to accurately measure monoterpene and sesquiterpene emissions. Together, these results provide the first leaf- and canopy-level isoprenoidmeasurements from the Amazon Arc of Deforestation and reveal a shift toward monoterpene- and sesquiterpene-dominated emissions. This shift has important implications for atmospheric chemistry, air quality, and carbon cycling—processes that remain underrepresented in Earth system models for this rapidly changing region.