Speaker
Description
Montane grasslands play a vital role in regional water cycling and agricultural productivity, yet their response to climate change remains insufficiently understood. This study presents findings from a multi-year climate manipulation experiment in the Austrian Alps, where high-precision lysimeters combined with warming (+3 °C) and elevated CO₂ concentrations (+300 ppm) were used to assess changes in evapotranspiration (ET), soil moisture, seepage, and biomass yield. A modeling framework based on HYDRUS-1D and Penman–Monteith formulations was applied to extrapolate results across scales. Elevated CO₂ consistently reduced ET and increased seepage due to partial stomatal closure, despite no significant change in leaf area index. In contrast, warming increased ET and reduced groundwater recharge, particularly during dry spells. When combined, the CO₂-induced water-saving effect only partially offset the warming-induced losses. Drought years (2018–2020) revealed strong yield reductions under ambient and warmed conditions, while elevated CO₂ mitigated these effects. Additional isotope tracing experiments using deuterium-labeled water showed altered post-drought soil water transport under combined warming and CO₂ enrichment, with reduced mixing and delayed infiltration. Upscaling using multiple hydrological models revealed differing sensitivities at plot and catchment scale, emphasizing the need for multi-model approaches in future impact assessments. Our results underline the importance of incorporating vegetation response to CO₂ in ecohydrological models and suggest that montane grasslands may provide limited resilience to climate-driven shifts in water availability.
