Can we bring alpine climate into ecotrons?

Abstract

Climate change is advancing at an unprecedented pace, impacting terrestrial ecosystems, particularly those in alpine regions. Consequently, there is a growing need to comprehend the associated impacts, underlying mechanisms, and implications. Long-term monitoring may face challenges in capturing the effects of accelerated climate change, and in-situ experiments in remote alpine areas often grapple with logistical constraints. Furthermore, attributing vegetative responses to specific manipulated variables proves challenging, especially under extreme alpine conditions such as low atmospheric pressure, low temperatures, or high radiation levels. Using a specially designed ecotron called 'TerraXcube' (Bozen, Italy), we investigated the feasibility of realistically reproducing harsh alpine conditions and explored the interactions among various parameters. For our measurements, we equipped the chamber with temperature and relative humidity probes, a spectrometer, barometer, and anemometer positioned at different heights within the chamber. We tested the spatial and temporal homogeneity of the variables— atmospheric pressure, temperature, relative humidity (RH), and radiation—independently, as well as their interactions over time and in space, by simulating various realistic alpine climatic scenarios. The measurements, conducted between -20°C and +25°C with relative humidity ranging from 10% to 95%, yielded satisfactory results. Over several hours, the largest difference at a specific position was 0.6°C and 4.3% RH, while the maximum difference between two sensors simultaneously was 1°C and 7% RH. At a height of 170 cm, the LED system emitted radiation at an intensity of 1,002 W/m² within the wavelength range of 280 to 900 nm; however, with a sharp decrease in intensity from the light source. The photosynthetically active radiation (PAR) at the chamber's center reached 1,883 μmol·m−2·s−1, achieving 77% of the potential annual maximum measured at 2,400 m a.s.l. This enables us to replicate the PAR level for 97% of the days throughout the year. Despite the high light intensity, the heating effect of the LED system was limited to a maximum of 2°C in the upper 40cm of the chamber. Pressure manipulation, with the highest technical demand, nonetheless resulted in high temporal homogeneity up to 4,000m a.s.l., corresponding to 618.9 mbar. In conclusion, the results emphasize the potential and utility of ecotrons in simulating a suitable climate for alpine ecological experiments. However, as in many ecotrons, it is crucial to acknowledge that minor island effects and irregularities are inevitable. Even more sophisticated parameters such as wind effects or pollinator function are currently not sufficiently addressed. A combined in- and outdoor usage of mobile field lysimeters might be a further step to bridge this gap between experimental results obtained in ecotrons and in the field.