Heatwaves Suppress Isoprene Emission Optima in Subtropical Eucalyptus: Implications for Biogenic VOC Modeling Under Extreme Thermal Events

Abstract Isoprene emissions from tropical plants under moderate conditions are more temperature‐sensitive than temperate plants and current model predictions. However, the effect of extreme heatwaves on this sensitivity remains uncertain. Here, we present controlled measurements of isoprene temperature responses for a subtropical eucalyptus species, revealing a surprising shift during heatwaves. During non‐heatwave periods, isoprene emissions followed established temperature sensitivity patterns with a well‐defined optimum temperature ( T opt ); However, heatwaves restricted plant physiological processes, resulting in an unexpected decrease in T opt . Current models, which consider acclimation effect based on long‐term temperature averages, failed to capture this shift, predicting higher T opt values during heatwaves. Remarkably, simulations using the default model curve that assumes no acclimation accurately replicated the observed isoprene emissions under both non‐heatwave and heatwave conditions. Our findings highlight the potential for extreme heat to suppress isoprene emissions in tropical regions and the need to reconsider isoprene‐temperature relationships under future climate.