Plant volatile emissions experiments with coniferous and broadleaf tree seedlings: the impact of extreme events and future climate scenarios

Biogenic volatile organic compounds (BVOC) are a highly complex and highly diverse set of chemicals emitted into the atmosphere by the Earth's biosphere. They affect atmospheric composition of trace gases such as the mixing ratios of methane, carbon monoxide, and tropospheric ozone through their atmospheric oxidation. Atmospheric oxidation products also lead to formation of atmospheric aerosol, which plays a crucial role in defining Earth's radiative balance and impacts air quality.  

Further increases in the average global temperature are expected for the following decades, with warmer and dryer conditions for Alpine regions. Warm winters appear to lead to earlier leaf-out. This may put trees at higher risk of late frost in spring. Thus, in addition to long-term changes in abiotic factors (temperature, water availability), the frequency of stress and double-stress events, such as a late spring frost and an extreme summer drought occurring in the same year, is expected to increase. How trees respond to such changes in abiotic factors and to abiotic (double) stress regarding their BVOC emissions composition and quantities is critical in understanding how atmospheric chemistry and SOA properties may be impacted.  

During the summer of 2022, we studied the impact of elevated temperatures (heat), reduced water availability (drought), extreme events (early spring frost) and double stress (early spring frost followed by extreme summer drought) on tree seedlings i.) BVOC precursors in plant tissues (i.e., secondary metabolites) and ii.) BVOC gas-phase emissions. To this end, i.) we developed an analytical method for extraction and chromatographic separation of secondary metabolites from plant tissues, and ii.) we designed and built a novel plant chamber for BVOC gas-phase measurements online with a PTR-ToF-MS and offline with thermodesorption-GC-MS. We will present comprehensive results from experiments with Scots Pine, Beech, and Oak seedlings under various abiotic stress conditions. Our findings provide crucial insights for improving estimations of future BVOC emissions and their atmospheric impacts.