Scots pine (Pinus Sylvestris) seedlings BVOC emissions composition under basal,  heat and drought conditions

Climate models project a further increase in the average global temperature for the following decades, with Alpine regions (and their ecosystems) expected to be over-proportionally more affected. Biogenic volatile organic compounds (BVOCs) comprise the largest, most highly complex, and diverse fraction of the volatile organic compounds (VOCs) emitted into the atmosphere (1). By emitting BVOCs, plants communicate, fight herbivores, and attract pollinators (2). It is well known that biotic stressors (e.g., insects feeding on plants) lead to changes in plants' BVOC emissions: certain compounds can be promoted, and others reduced. Atmospheric oxidation of BVOCs affects the concentration of methane, carbon monoxide, and tropospheric ozone, leading to the formation of Secondary Organic Aerosol (SOA). Atmospheric aerosol load is crucial in defining the radiative balance and negatively impacts air-quality standards (3). Stress-induced changes in plant emissions may thus lead to changes in atmospheric chemistry and SOA properties (e.g., ref. 4). The impact of prolonged changes in abiotic factors and abiotic stress (e.g., heat and drought) on plants' BVOC composition and emissions quantities, and how this may impact atmospheric chemistry and SOA properties, need to be better understood.  Within the experimental project "Acclimation and environmental memory” (AccliMemo), we study BVOC composition and quantities at basal conditions and under prolonged heat and drought. To this purpose, Scots pine (Pinus Sylvestris) seedlings were grown from seeds collected from selected mother trees from the long-term irrigation experiment Pfynwald. Those mother trees experienced different long-term water availability. This also allows us to examine the consequence of transgenerational memory on BVOC emissions (5).  Our conference contribution will give insight into our findings from plant chamber experiments and address i) gas-phase BVOC samples collected on sorbent tubes and analyzed by Thermal Desorption GC-MS and ii) gas-phase BVOC measurements collected in-situ using a PTR-ToF-MS. These data provide a well-resolved picture of terpene compositions and diurnal trends in emission levels. The BVOC analysis in the gas phase is complemented by a detailed analysis of the secondary metabolites in needle samples. Secondary metabolites are extracted in organic solvents and analyzed by liquid injection GC-FID/MS.  Bibliography  (1) Sindelarova, K., Granier, C., Bouarar, I., Guenther, A., Tilmes, S., Stavrakou, T., Müller, J.-F., Kuhn, U., Stefani, P., and Knorr, W.: Global data set of biogenic VOC emissions calculated by the MEGAN model over the last 30 years, Atmospheric Chem. Phys., 14, 9317–9341, https://doi.org/10.5194/acp-14-9317-2014, 2014. (2) Niinemets, Ü. and Monson, R. K. (Eds.): Biology, Controls and Models of Tree Volatile Organic Compound Emissions, Springer Netherlands, Dordrecht, https://doi.org/10.1007/978-94-007-6606-8, 2013. (3) Seinfeld, John H. and Pandis, Spyros N.: Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, 3rd Edition., Wiley, 1152 pp., 2016. (4) Smith, N. R., et al.: Viscosity and liquid–liquid phase separation in healthy and stressed plant SOA, Environ. Sci. Atmospheres, 1, 140–153, https://doi.org/10.1039/D0EA00020E, 2021. (5) Bose, A. K., et al.: Memory of environmental conditions across generations affects the acclimation potential of scots pine, Plant Cell Environ., 43, 1288–1299, https://doi.org/10.1111/pce.13729, 2020. Funding: Swiss National Science Foundation, Project Numbers 189109, 199317, and, 194390.