Abstract ID: 3.12167 | Accepted as Poster | Talk | TBA | TBA

One consequence of climate change on plant distribution in alpine areas is the observed shift of plants towards higher elevations as they track their thermal niches. As plants migrate, they encounter new environmental conditions that could represent a challenge for their growth and survival. One less-studied factor at higher elevations is the reduced air pressure. Our objective was to elucidate the direct effect of reduced air pressure on the ecophysiology of plant species across an elevation gradient ranging from 1500 m to 4000 m, corresponding to air pressures of 85 kPa and 60 kPa, respectively. We selected two plant species, Hieracium pilosella (Asteraceae) and Trifolium pratense (Fabaceae), that we collected from a perennial montane grassland at 1500 m within the Long-Term Socio-Ecological Research (LTSER) site in Matsch/Mazia, Italy. Our study was conducted in an extreme climate simulation infrastructure capable of controlling crucial environmental parameters (TerraXcube center). The experiment lasted for one month, after which we determined photosynthesis, chlorophyll fluorescence, growth, carbohydrates, carbon stable isotopes, and plant nitrogen concentrations. Generally, reduced air pressure leads to a decrease in the partial pressure of all atmospheric gases, potentially depriving plants of CO₂ and O₂. Our results showed a decrease in growth parameters and chlorophyll content at lower air pressure, along with a higher abundance of ¹³C, higher photosynthetic efficiency and an accumulation of total non-structural carbohydrates in the leaves of both plant species. These findings suggest that plants at high elevations could suffer from low O₂, and that carbon is not a limiting factor for their growth and performance under our experimental conditions. The magnitude of these effects varies depending on the plant species. We conclude that reduced air pressure could specifically influence the distribution pattern of plant species in alpine areas.