Regional Mountain Conference

Climate change is projected to increase drought frequency and severity in alpine regions, significantly affecting plant physiological processes, ecosystem functioning and the ecosystem’s exchange of biogenic volatile organic compounds (BVOCs) with the atmosphere. BVOCs influence atmospheric chemistry, air quality, and climate feedbacks. While constitutive BVOC emissions are well-characterized, drought-induced changes remain poorly constrained, limiting predictions under future climate scenarios.

We quantified gas exchange in two alpine conifers – Pinus sylvestris and Juniperus communis – exposed to four drought intensities for four weeks at the VOC-SCREEN facility at the Helmholtz Center Munich. Continuous PTR-ToF-MS measurements, complemented by bi-weekly GC-MS analysis, resolved temporal dynamics of BVOC emissions, while CO₂-assimilation and transpiration were measured using non-dispersive infrared sensors.

The species exhibited contrasting carbon strategies under severe drought: P. sylvestris maintained positive carbon balance while J. communis experienced net loss. Total monoterpene emissions were largely drought-insensitive, though compound-specific regulation occurred in P. sylvestris. Sesquiterpenes were strongly drought-induced for both species, but with differing temporal patterns between the species: sustained in J. communis, bell-shaped in P. sylvestris. Methyl salicylate responses were opposite between species, highlighting compound-specific stress signaling.

These results demonstrate that BVOC drought responses reflect species-specific carbon balance and physiological thresholds, providing crucial constraints for atmospheric chemistry models under climate change.