Contrasting Emission Seasonality Between Light‐Dependent and Light‐Independent Biogenic VOCs From Subtropical Eucalyptus Trees

Abstract Biogenic volatile organic compounds (BVOCs) from terrestrial vegetation play a significant role in atmospheric chemistry and climate regulation. However, the seasonality of BVOC emissions, especially from tropical and subtropical plants, remains poorly understood. This study investigated the seasonal variation in BVOC emissions from Eucalyptus urophylla , a common subtropical species, through in situ measurements during dry and wet seasons. We observed a marked seasonality in emission factors ( E s ), with light‐dependent BVOCs exhibiting increased emissions from the dry to wet season, while light‐independent BVOCs showed a decline. Isoprene emissions followed temperature‐driven patterns, with substantial increases in the wet season, while the seasonal dynamics of monoterpenes (MTs), particularly β ‐ocimenes, exceeded model predictions, indicating more complex emission behaviors. Growth temperature was identified as the primary driver of these seasonal variations, with temperature sensitivity differing between light‐dependent and light‐independent compounds. Our results also suggest that the tropical/subtropical plants may emit more light‐dependent, highly reactive BVOCs in the hot wet season to protect plant leaves from damage by heat‐induced reactive oxygen species. Our study implies that BVOC emissions from subtropical vegetation are highly responsive to seasonal temperature changes, with significant implications for atmospheric reactivity and biosphere‐atmosphere interactions, highlighting the need for improvements in current emission models to better account for the complex seasonality of BVOCs, particularly MTs, in tropical and subtropical ecosystems.