Questions: The 1990s were the warmest decade since the beginning of climate measurements. Based on almost 100 years of monitoring in the Swiss Alps, we asked (1) whether the extraordinary warm climatic conditions of the 1990s are reflected in the floristic composition of Alpine summit vegetation and, if so, (2) what the magnitude and rate of species change has been over the last few decades compared to the documented increase in species richness within the first 80 years of the 20th century.
Location: Ten high mountain summits of the Bernina area in the southeastern Swiss Alps.
Methods: Resurvey of the floristic composition of the uppermost altitudinal 10 m of these summits, applying the same methodology of former two surveys (1905 and 1985) and recording the presence of all vascular plant species.
Results: Whereas the continued increase in plant species richness of high alpine summit vegetation is confirmed, our results also suggest an acceleration of the trend in the upward shift of alpine plants.
Conclusion: Vegetation change in the southeastern Swiss Alps has accelerated since 1985, consistent with a climate change explanation.
Nomenclature: Lauber & Wagner (1998). Verification of synonyms was based on Hess et al. (1984) and the Swiss Web Flora ( www.wsl.ch/land/products/webflora/floramodul1-en.html).