One century of vegetation change on Isla Persa, a nunatak in the Bernina massif in the Swiss Alps

Authors

  • Pascal Vittoz,

    Corresponding author
    1. Faculty of Geosciences and Environment and Department of Ecology and Evolution (Faculty of Biology and Medicine), University of Lausanne, Bâtiment Biophore, CH-1015 Lausanne, Switzerland;
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  • Jeanne Bodin,

    1. Institute of Geobotany, Leibniz University of Hannover, Nienburger Str 17, DE-30167 Hannover, Germany;
    2. UMR INRA-UHP 1137 Forest Ecology and Ecophysiology Unit, Phytoecology team, INRA Nancy, FR-54280 Champenoux, France;
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  • Stefan Ungricht,

    1. University of Zurich, Institute of Systematic Botany, Herbarium, Zollikerstrasse 107, CH-8008 Zurich, Switzerland;
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  • Conradin A. Burga,

    1. Department of Geography, Physical Geography Division, University of Zurich-Irchel, Winterthurerstr. 190, CH-8057 Zurich, Switzerland;
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  • Gian-Reto Walther

    1. Institute of Geobotany, Leibniz University of Hannover, Nienburger Str 17, DE-30167 Hannover, Germany;
    2. Department of Plant Ecology, University of Bayreuth, DE-95440 Bayreuth, Germany;
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  • Nomenclature: Aeschimann et al. (2004).

  • Acknowledgements. This research was supported by the Federal Office for the Environment FOEN (Switzerland), the Fondation Herbette (University of Lausanne) for P. Vittoz, by the DFG (German Research Foundation), project WA 1523/6–1 for G.-R. Walther and by the EC within the FP 6 Integrated Project ‘ALARM’ (GOCE-CT-2003–5006675) for J. Bodin. We thank J. Barkowski, S. Beißner, S. Berger, E. Frei & S. Jutzeler for participation in the field work and J.-P. Müller (Chur/CH) and the staff of the library of St. Moritz for providing historic literature. We also thank R. Reinalter (Brail/CH) for help with the identification of plant species and R.H. Økland, H. Pauli and a referee for comments on an earlier version of the manuscript.

Corresponding author; Fax +41 216924265; E-mail pascal.vittoz@unil.ch

Abstract

Abstract

Question:

How did the vascular plant species composition of a nunatak in the alpine vegetation belt change over a time span of 100 years?

Location:

A 5.6-ha nunatak, Isla Persa in the Swiss Alps, that remained ice-free during the last maximum glacier advance in the 1850s and is today partly covered with climactic alpine grassland and dwarf heath shrubs.

Methods:

Floristic inventories in 1906, 1927, 1972, 1995, 2003 and 2004 and a comparative analysis of the species composition over the period 1906–2004.

Results:

31 species that were not recorded in the first inventory were found in the following surveys. However, among them only six were common by 2004. Generally, the new species prefer warmer conditions than those previously present and most newcomers are associated with montane or sub-alpine grasslands and woodlands. In particular, the observed increase of Vaccinium myrtillus and the arrival of shrub and tree species further substantiate a trend towards vegetation composition of the lower altitudinal belt. Ferns represented 26% of the newcomers, probably due to the high dispersal ability of their lightweight spores. The observed species enrichment was globally small compared to previously inventoried summits.

Conclusion:

Floristic change strongly suggests warmer climatic conditions as the main factor contributing to species compositional change. The relative stability of species richness may be explained by several factors: the isolation of the nunatak and the difficulties for plants to reach the site, the colder local climate, a limited available species pool and interactions of established alpine plants with newly immigrating taxa. Supplementary data collected at a similar altitude would be necessary to better understand the influence of climate change on alpine grasslands.

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