Abstract ID: 3.12708 | Accepted as Talk | Talk | TBA | TBA

In alpine ecosystems, climate change forces species to respond by either adapting their life strategies to the new conditions or migrating upwards to higher elevations to match their thermal preferences. While migrating upward allows organisms to maintain stable temperature, it exposes them to reduced atmospheric pressure, affecting key physical parameters such as vapor pressure deficit, CO2 partial pressure, and gas diffusion. These changes can impact not only plant physiology but also microbial communities that interact with plants. Within the international project ‘Upshift’ we investigate the direct and indirect effects of reduced atmospheric pressure on upward-migrating plants and soil microorganisms. Three test plants (Brachypodium rupestre (grass), Hieracium pilosella (forb), and Trifolium pratense (legume)) were collected from a perennial montane grassland at 1500 m within the Long-Term Socio-Ecological Research site (LTSER) Matsch/Mazia (Italy) and transferred to the terraXcube device, which allows to disentangle altered atmospheric pressure from other parameters like temperature and humidity. Plants were exposed to pressures simulating 260, 1500, 2500, and 4000 m a.s.l. After several weeks and alongside eco-physiological plant measurements, rhizosphere soil was collected and analyzed for microbial composition and activity. Our results prove plant-specific effects of atmospheric pressure on microbial parameters. Whereas reduced air pressure caused an increase in microbial biomass in the rhizosphere of B. rupestre and T. pratense a decrease was observed with H. pilosella. For B. rupestre and H. pilosella these results were confirmed for the activity of dehydrogenase in the rhizosphere. Also, microbial communities were affected by atmospheric pressure. The rhizosphere community of B. rupestre grown under the highest atmospheric pressure (lowest elevation) differed most from all other samples, whereas T. pratense showed the strongest divergence at the lowest pressure (highest elevation). H. pilosella exhibited significant differences between prokaryote communities at the two high vs. the two low pressures. All proven effects were independent from possible changes of plant physiology and growth. These findings represent the first evidence of isolated atmospheric pressure effects on soil microbial communities under controlled conditions.