El Niño heat extremes suppress soil isoprene uptake capacity in the Amazon rainforest

Soils are recognized sinks for atmospheric isoprene, but their in-situ behavior remains understudied, particularly in the Amazon where emissions are globally significant. Here we show how the 2023 El Niño affected the diel and seasonal variation in soil isoprene fluxes. Under regular conditions, the soils acted as a persistent isoprene sink, with uptake driven primarily by ambient isoprene mixing ratios, following a diel cycle and peaking during the dry season. Soil organic content and litter modulated the fluxes by shaping moisture, temperature, and gas-diffusion responses. Isoprene uptake capacity and soil respiration peaked at ~27% soil water content and 26.5 °C soil temperature. El Niño heat extremes, suppressed soil respiration, and soil isoprene uptake capacity declined 4.3‑fold. As climate change intensifies heat extremes, reduced soil isoprene uptake capacity could shift atmospheric oxidation, aerosol formation, and methane lifetime. Incorporating soil isoprene uptake into atmospheric models is essential for quantifying these feedbacks.