Bringing mountains into the lab: evaluating ecotron performance for simulating alpine climate extremes

Abstract Background Mountain ecosystems are highly sensitive to climate change, making them key indicators of environmental shifts. Studying these environments experimentally, however, is challenging because harsh conditions, remote field sites and high natural variability make alpine research logistically demanding and time-consuming. This complexity often limits the attribution of ecological responses to individual drivers. To address these limitations, controlled-environment facilities offer powerful platforms for ecological and physiological research, but their ability to simulate the combined extremes of alpine climates – low temperatures, high radiation (including UV) and reduced air pressure – has rarely been quantified. The magnitude of inherent chamber effects, particularly under combined alpine extremes where they are likely amplified, also remains poorly characterized. A systematic evaluation of realistic multi-driver climate simulations is therefore essential for designing reproducible and physiologically meaningful experiments. Results We assessed the accuracy and spatial structure of key abiotic drivers—temperature (− 20 to + 25 °C), relative humidity (RH; 10–95%), irradiance (up to 2500 µmol m⁻² s⁻¹), and atmospheric pressure (616–983 mbar)—under both isolated and combined scenarios. Setpoints were reproduced with high temporal stability (± 0.5 °C and ± 4% RH). Even under combined low pressure and full illumination, spatial variation remained moderate (≤ 1.3 °C and ≤ 7.1% RH). Vertical irradiance decreased by ~ 45% between 240 and 33 cm height, while horizontal spectral composition remained homogeneous up to 170 cm. In dedicated interaction experiments, increasing irradiance from 50% to 100% LED output raised air temperature by ~ 0.6–1.1 °C, whereas RH responses depended strongly on air exchange: RH decreased by ~ 11.0–13.3%-points under low fresh-air supply (10 m³ h⁻¹) but only by ~ 3.9–6.0%-points under high fresh-air supply (50 m³ h⁻¹). Pressure control was accurate and only weakly coupled to other variables. Conclusions Our analysis quantifies the magnitude and structure of chamber effects that occur when simulating alpine climate extremes in controlled environments. By relating these artefacts to specific design and air circulation conditions, the study offers practical guidance for minimizing biases and improving reproducibility in ecotron experiments. These results contribute to refining controlled-environment approaches for realistic high-elevation climate simulations.