Global Variability in Isoprenoid Emissions: Divergent Responses to Warming and Drought Driven by Physiochemical...

Climate change alters biogenic volatile organic compound (BVOC) emissions, yet a quantitative understanding of the interactive effects of warming and drought across plant types and physiological mechanisms remains limited. Here, we quantify the impacts of warming and drought on isoprene and monoterpene (MT) emissions through a meta-analysis of field and greenhouse experiments, complemented by machine learning simulations, and map their spatial distribution. Globally, warming increased isoprene and MT emissions by 107% and 60%, respectively, while drought reduced them by 27% and 33%. Combined warming and drought increased MT emissions by 37%. Neither warming nor drought had a significant effect on sesquiterpene (SQT) emissions. Warming-induced increases in isoprene emissions were positively correlated with changes in photosynthetic electron transport rate (J_f), whereas MT responses declined at higher mean annual temperatures. Under drought, although decoupled from photosynthesis, the responses of both compounds remained positively associated with those of stomatal conductance (g_s). Spatially, global 1°C warming elicited the strongest responses in isoprenoid emissions at high altitudes/latitudes (e.g., Siberian Plateau, Arctic, and Tibetan Plateau). Under a low-warming scenario (SSP1-1.9), responses resembled historical trends, while a high-warming scenario (SSP5-8.5) amplified isoprene emissions in C₄ vegetation-dominated regions and suppressed MT responses in boreal coniferous forests. Our findings reveal distinct physiological controls: isoprene exhibits thermal resilience, MT remains temperature-sensitive, and both compounds are regulated by g_s during drought. These response patterns vary significantly with plant functional type, experimental design and duration, and initial climate conditions. These mechanistic insights can inform the selection of plant speciesand adaptation strategies for vulnerable ecosystems, thereby helping to mitigate air quality and climate feedbacks under future warming and drought conditions.