Stress is in the air: BVOC emissions from beech and oak trees under combined heat stress and herbivory feeding

Biogenic Volatile Organic Compound (BVOC) emissions account for more than 70% of VOC global emissions and play a significant role in atmospheric chemistry due to their high reactivity. These compounds are naturally emitted by trees as they are involved in ecological processes such as plant communication and defense against biotic and abiotic stressors. However, climate change has increased those stress factors for trees, altering both magnitude and composition of BVOC emissions. Once oxidized in the atmosphere, BVOCs contribute to the production of Secondary Organic Aerosols (SOA) which are involved in cloud formation, mitigating the Earth’s radiative balance and impacting air quality. Investigating how emission rates and compositions are impacted by such stressors is essential in understanding how atmospheric chemistry is affected.

So far, most studies focused on coniferous trees and isolated stress factors, leaving broad-leaved trees and combined stress impacts understudied, although common. To address the gap, this study sheds light on the BVOC emissions from two common deciduous tree species in Europe: English oak (Quercus Robur), an isoprene emitter, and European beech (Fagus Sylvatica), a monoterpene emitter. They were successively exposed to herbivory feeding of gypsy moth larvae (Lymantria Dispar Dispar) then both herbivory and heat stress (up to ~40°C).

To quantify BVOC fluxes, the emissions were sampled from a climate-controlled plant-chamber (SAPHIR-PLUS) by PTR-TOF-MS coupled to a fastGC. Temperature ramp experiments were conducted under each condition to study the temperature sensitivity of terpenoid emissions in response to the different stressors.

Here, we present results from an intensive two-month campaign with focus on the main primary BVOC emissions. Preliminary results indicate that herbivory feeding increased monoterpenes emissions, but heat stress induced a stronger burst in emissions for both tree species, highlighting their role in plant defense response.