Snow Gum Dieback Enhances Trunk Monoterpene Emissions in the Australian Alps

Abstract Canopy decline is increasingly prevalent in high‐elevation snow gum ( Eucalyptus pauciflora ) forests across the Australian Alps. This phenomenon, known as snow gum dieback, is associated with infestations by the wood‐boring beetle, Phoracantha mastersi . The larvae of this beetle create feeding galleries in the tree trunk, leading to the exudation of kino, a tannin‐rich resin produced as a defense response. Kino could be a significant source of volatile organic compounds (VOCs), a group of reactive gases that influence atmospheric chemistry contributing to climate feedbacks. As dieback progresses, increased kino exudation might enhance VOC emissions, yet the magnitude and composition of dieback‐associated VOCs remain completely unexplored in this system. Here, we quantify VOC emissions from snow gum trunks and leaves in both infested and healthy trees. Additionally, we measure the temperature response of VOC emissions from kino and bark of infested trunks. We show that the magnitude of VOC emissions from damaged trunks (217 ± 104 μg m −2 h −1 ) is comparable to that from foliage (290 ± 61 μg m −2 h −1 ). Infested trunks exhibited a seven‐fold increase in VOC emissions relative to healthy ones, predominantly driven by a ∼62‐fold increase in monoterpene emissions. Moreover, the emissions from both kino and bark increased with temperature. In contrast, leaves showed no differences in VOC emission rates or blends between healthy and infested trees. These findings are crucial for understanding the ecological and atmospheric consequences of snow gum dieback and can help improve estimates of forest carbon budgets under a changing climate.