Climate change drives plant compositional changes in alpine snow-bed communities: a 10-year study in the Monte Rosa massif

Ginevra Nota ¹, Simone Ravetto Enri ¹, Giacomo Marengo ¹, Giampiero Lombardi ¹, Michele Lonati ¹

Department of Agriculture, Forest and Food Sciences, University of Torino, Largo Paolo Braccini 2, 10095 Grugliasco (TO) ¹

Alpine snow-bed vegetation communities develop in high-elevation (> 2500 m a.s.l.) flat depressions with prolonged snow cover and deep soils rich in organic matter. Long-lasting snowpack protects plant species from freezing damage but also constrains them with a short growing season, leading to the differentiation of snow-bed plant specialists. Climate change is considered an important driver of change for snow-bed communities due to rising air temperatures, earlier snowmelt, and the consequent extension or shift of the growing season. Previous research has shown that most snow-bed species can potentially adapt to such changes, as they have a phenological plasticity able to track snowmelt dates (Crepaz et al. 2024; Quaglia et al. 2020). However, it remains uncertain whether changes in environmental conditions could alter community composition by giving other species a competitive advantage over snow-bed plants. We annually surveyed the botanical composition of seven snow-bed sites (Salicetum herbaceae association) in the Cimalegna plateau (Monte Rosa Massif, NW Italian Alps, 2680-2850 m a.s.l.) over a 10-year period (2015-2024) using the point intercept method on permanent plots. The average temperature and length of the snow-free season during the study period were 5.3 °C and 122 days, respectively, with 2022 showing an anomalous 33-day advancement in the season compared to the average. To investigate the changes in plant composition, the relative abundance of snow-bed, oligotrophic grassland, eutrophic grassland, and scree species (according to their phytosociological optimum), and of individual species were calculated and the trends analyzed with Generalized Linear Mixed Models. Results indicated an overall significant increase in oligotrophic grassland species (+6.9%) and a decline in scree species (-4.2%), while snow-bed and eutrophic grassland species remained stable. Agrostis rupestris was the oligotrophic grassland species showing the highest increase (+3.5%), while Ranunculus glacialis was the scree species declining the most (-1.4%). Noteworthy, the increase in oligotrophic species was more pronounced in the anomalous year 2022, associated with a decrease, although not significant, of snow-bed species. Our findings showed that snow-bed communities are undergoing slow but progressive and directional plant compositional changes towards an increase in grassland species and a reduction of scree species. Such changes likely reflect community response to climate change and more specifically to the advancement and extension of the snow-free growing season. Therefore, we conclude that snow-bed species, despite being able to adapt their phenology to changing environmental conditions, may face competition from grassland species in the long-term. Crepaz H, Quaglia E, Lombardi G, Lonati M, Rossi M, Ravetto Enri S, Dullinger S, Tappeiner U, Niedrist G. Phenological responses of alpine snowbed communities to advancing snowmelt. Ecology and Evolution 14(7): e11714 Quaglia E, Ravetto Enri S, Perotti E, Probo M, Lombardi G, Lonati M. Alpine tundra species phenology is mostly driven by climate-related variables rather than by photoperiod. Journal of Mountain Science 17(9): 2081-2096

Main author career stage: Postdoc / Fellow

Contribution type: Talk

First choice session: 2. Ecology

Second choice session: 3. Biodiversity and global change