Long-term climate manipulation experiment in a high-alpine soil reveals functional and microbial community shifts

Climate change threatens ecosystems worldwide through rising temperatures and altered environmental ecosystems, affecting all organisms, including the microorganisms that regulate biogeochemical cycles and greenhouse gas emissions. These microbial communities play essential roles in nutrient turnover, soil formation, and ecosystem stability, making their responses to climate-driven disturbances critical for predicting future ecosystem functioning. Despite their importance, long-term field experiments investigating how microbial assemblages respond to global change factors—such as warming, altered precipitation patterns, and shifts in vegetation—remain scarce. This scarcity is especially pronounced in high-alpine environments, where harsh climatic conditions, steep environmental gradients, and logistical challenges limit the establishment and maintenance of sustained ecological studies. To address this knowledge gap, we conducted a long-term field experiment for 10 years in the Damma glacier forefield (Switzerland) to assess prokaryotic and fungal community dynamics and ecosystem functions (e.g. greenhouse gas emissions). We simulated two climate change scenarios: experimental warming (~2°C) using open-top chambers (OTCs) and precipitation reduction (~30%). Through image analysis, we found that vegetation cover was significantly higher under warming and precipitation reduction compared to the control. Also, we observed significant treatment effects on CO₂, N₂O, and CH₄ fluxes. Warming and reduced precipitation significantly increased CO₂ emission rates (µmol m⁻² day⁻¹) under both light and dark conditions. In contrast, N₂O emissions showed no significant changes across treatments, while CH₄ fluxes were significantly reduced under light conditions with warming and under dark conditions with reduced precipitation. These changes in greenhouse gas fluxes were accompanied by shifts in microbial community structure: alpha diversity metrics (richness and Shannon index) for both prokaryotes and fungi exhibited significant treatment-by-year interactions, whereas beta diversity was significantly affected by both treatment and year but without treatment-by-year interactions. This suggests that warming and precipitation reduction generate stable compositional differences between microbial communities that persist across years. Collectively, our findings highlight the importance of long-term, multi-year monitoring to accurately assess microbial and ecosystem responses to climate change.