Emissions of isoprene and monoterpenes from urban tree species in China and relationships with their driving factors

Isoprenoid (ISOP) emissions, particularly isoprene and monoterpenes, can significantly affect local and regional air quality due to their high chemical reactivity, with hot spots over polluted megacities. We investigated ISOP emissions from 32 common woody species in Beijing (Northern China) and Nanjing (Southern China). Relationships of ISOP emissions with plant functional types (trees vs shrubs; evergreen vs deciduous), leaf textures (papery vs leathery) and leaf physiological and biochemical traits were studied. Twenty-seven species emitted ISOPs, spanning very high isoprene emissions (typical of deciduous trees with papery leaves) to minute emissions of isoprene and monoterpenes in leathery leaves. Significant positive relationships between isoprene emission and the amounts of chlorophyll content, isoprene synthase protein and leaf nitrogen were observed, while the emissions of monoterpenes were not significantly related to any leaf physiological or biochemical trait. While looking for factors driving leaf isoprene and monoterpene emissions are complicated, our study shows leaf papery texture and high chlorophyll content may indicate presence of high isoprene emitters, to be used with caution for urban greening purposes.