A common soil temperature threshold for the upper limit of alpine grasslands in European mountains Bürli, Sarah Fernández-Calzado, Rosa Molero Mesa, Joaquín Alpine life zone GLORIA Growing season Plant-Climate interactions Soil temperature Vascular plants Open Access funding provided by Université de Lausanne. Field inventories and temperature loggers were financially supported by 5th RTD Framework Programme of the European Union, UK Centre for Ecology and Hydrology, Département de la culture et des sports du Valais, Departamento de Medio Ambiente del Gobierno de Aragón, Foundation Dr. Joachim de Giacomi, Fondation Mariétan, Italian project of strategic interest NextData, MAVA Foundation, Frignano Regional Park (Modena), Norwegian Environment Agency, Ordesa & Monte Perdido National Park, Research Commission of the Swiss National Park, Scientific Grant Agency VEGA (project Nr. 2/0132/18), Scottish Natural Heritage, Sierra Nevada National Park, Société académique de Genève, Swiss Federal Office of Education and Science, Swiss Federal Office for the Environment, Tiroler Wissenschaftsfonds, Tuscan-Emilian Apennines National Park, and Wissenschaftsförderung der Südtiroler Landesregierung. We thank the numerous collaborators in each region who participated in field inventories, S. Jordan for his preliminary analyses, and A.-L. Aeby and F. Schütz for their assistance on statistical analyses. We are particularly grateful to C. Körner and two anonymous reviewers for their helpful comments on earlier versions of the manuscript. While climatic research about treeline has a long history, the climatic conditions corresponding to the upper limit of closed alpine grasslands remain poorly understood. Here, we propose a climatic definition for this limit, the 'grassline', in analogy to the treeline, which is based on the growing season length and the soil temperature. Eighty-seven mountain summits across ten European mountain ranges, covering three biomes (boreal, temperate, Mediterranean), were inventoried as part of the GLORIA project. Vascular plant cover was estimated visually in 326 plots of 1 x 1 m. Soil temperatures were measured in situ for 2-7 years, from which the length of the growing season and mean temperature were derived. The climatic conditions corresponding to 40% plant cover were defined as the thresholds for alpine grassland. Closed vegetation was present in locations with a mean growing season soil temperature warmer than 4.9 degrees C, or a minimal growing season length of 85 days, with the growing season defined as encompassing days with daily mean >= 1 degrees C. Hence, the upper limit of closed grasslands was associated with a mean soil temperature close to that previously observed at the treeline, and in accordance with physiological thresholds to growth in vascular plants. In contrast to trees, whose canopy temperature is coupled with air temperature, small-stature alpine plants benefit from the soil warmed by solar radiation and consequently, they can grow at higher elevations. Since substrate stability is necessary for grasslands to occur at their climatic limit, the grassline rarely appears as a distinct linear feature. 2021-04-22T12:37:43Z 2021-04-22T12:37:43Z 2021-03-04 info:eu-repo/semantics/article Bürli, S., Theurillat, JP., Winkler, M. et al. A common soil temperature threshold for the upper limit of alpine grasslands in European mountains. Alp Botany (2021). [https://doi.org/10.1007/s00035-021-00250-1] http://hdl.handle.net/10481/68059 10.1007/s00035-021-00250-1 eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España Springer