Air pressure effects on upwards shifting alpine ecosystems

For many organisms, climate change alters the maximum tolerable elevation and very often leads to an upward shift in occurrence. Montane organisms that migrate upwards to follow their thermal niche experience no temperature change, but have to cope with a reduced air pressure. This affects biologically relevant physical parameters such as vapor pressure deficit, CO2 partial pressure and gas diffusion, which in turn are involved in fundamental ecophysiological processes such as evapotranspiration, photosynthesis or respiration. These parameters have both direct effects on species and also indirect effects, as the way species and/or communities interact with each other might change. The effects of reduced atmospheric pressure on upward migrating plants and soil microorganisms and their novel associations are largely unknown, so that this hitherto neglected environmental issue urgently needs to be investigated. UPSHIFT will fill this knowledge gap by applying novel experimental approaches to study the effects of atmospheric pressure on ecophysiology and interactions between organisms. Our main goals are (i) to understand how upwards migrating soil microorganisms and plant species respond to lower atmospheric pressure, (ii) to assess how upwardly migrating soil microorganisms and plants interact with persistent plants and soil microorganisms and (iii) to assess the impact of lower air pressure on the water balance of the entire ecosystem. We will measure various ecophysiological, chemical and microbi al indicators to gain insight into fundamental processes such as water use, photosynthesis and growth. Our approach integrates a controlled environmental system of the next generation (terraXcube, Bozen) to simulate different alpine climatic conditions and to be able to investigate the effects of temperature and air pressure separately with pot and mesocosm (lysimeter) experiments. Finally, field experiments are carried out to evaluate the reliability of the results obtained. The UPSHIFT project is the first attempt known so far to determine the effects of atmospheric pressure on (micro)organisms in the context of climate change. This is of fundamental importance because of the upward migrating organisms and the profound consequences for the functioning of alpine ecosystems. UPSHIFT is based on a transnational cooperation between the Department of Microbiology at the University of Innsbruck (Paul Illmer) and the Institute for Alpine Environment at the Eurac Research, Bozen (Matteo Dainese).