Field-deployable branch enclosure system for biogenic volatile organic compounds emitted from conifers

Abstract. Biogenic volatile organic compounds (BVOCs), emitted primarily from terrestrial plants, significantly influence atmospheric chemistry and climate change. Conifers are major sources of BVOCs in temperate regions. However, their unique physiology, particularly the storage of terpenes within their tissues, makes accurate measurements of BVOC emissions challenging owing to contact-induced release. We developed a portable dynamic branch enclosure system specifically optimized for BVOC measurement in conifers, which enables measurements of multiple trees in a single day. The system uses filtered ambient air as a purge gas to reduce logistical challenges and features a foldable bag design to minimize excessive BVOC release induced by physical contact. It provides BVOC- and ozone-free air, maintains stable internal temperature and humidity conditions closely approximating those of natural environments, and ensures repeatable measurements of BVOC emissions. Field testing with Japanese cedar (Cryptomeria japonica) demonstrated the system's robust field performance, successfully capturing both significant inter-individual variability and the dynamic diurnal patterns of BVOC emissions. The system's ability to reliably resolve these differences under field conditions demonstrates its applicability for advancing our understanding of BVOC dynamics in diverse ecosystems.