Climate change effects on biological soil crusts in high-alpine regions: experimental setup and first insights

The Alps are warming at approximately twice the global mean rate, accompanied by altered precipitation regimes and rapid snow and ice loss. In high-alpine ecosystems, where low temperatures and short growing seasons constrain the establishment of vascular plants, biological soil crusts (biocrusts) form cohesive surface communities that can become a dominant biological component of the landscape. Composed of cyanobacteria, algae, lichens, and bryophytes, along with heterotrophic bacteria, archaea, and fungi, biocrusts play a key role in soil stabilization, water retention, and carbon and nitrogen cycling. Despite their ecological importance, biocrust responses to climate warming in alpine environments remain poorly understood.

To address this, we developed an integrated, field-based experimental framework to investigate alpine biocrust responses to climate change under realistic conditions in the high-alpine region of the Großglockner (Austria). The setup consists of a full-factorial design combining active infrared warming and manual snow-removal treatments. Biocrust responses are monitored using continuous meso- and microclimatic measurements, repeated image-based classification of surface cover using machine-learning methods, and complementary field sampling targeting DNA-based microbial community composition, nutrient availability, and soil aggregate stability.

The project was launched in May 2024. Following installation and optimization, the setup was fully operational throughout the 2025 growing season, providing a first complete field dataset for assessing warming effects on alpine biocrusts.

The experimental warming setup proved to work reliably under high-alpine conditions, with a minor decline in treatment performance towards the end of the growing season. Microclimatic measurements revealed that the warming treatment increased biocrust surface temperatures by approximately 3 °C and soil temperatures at a 5 cm depth by about 2 °C during most of the season, whereas mesoclimatic measurements captured the characteristic seasonal patterns of the high-alpine climate. Mapping of surface cover revealed pronounced seasonal dynamics in coverage, with vascular plants and mosses peaking and cyanobacteria-dominated crusts declining in the middle of the growing season, while lichen cover remained comparatively stable. More in-depth results on microbial composition and effects on nutrient availability are currently being analysed.

This novel experimental field setup improves our understanding of the resilience and functioning of alpine biocrusts under climate warming and their role in high-alpine ecosystem dynamics.