Changes in plant species richness over the last century in the eastern Swiss Alps: elevational gradient, bedrock effects and migration rates |
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Authors: | Barbara Holzinger Karl Hülber Martin Camenisch Georg Grabherr |
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Institution: | (1) Department of Conservation Biology, Vegetation and Landscape Ecology, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria;(2) V.I.N.C.A.—Vienna Institute for Nature Conservation and Analyses, Giessergasse 6/7, 1090 Vienna, Austria;(3) Camenisch & Zahner, Giacomettistrasse 119, 7000 Chur, Switzerland |
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Abstract: | Areas of 2,800–3,000 m a.s.l. represent the alpine-nival ecotone in the Alps. This transition zone connecting the closed swards
of the alpine belt and the scattered vegetation of the nival belt may show particularly strong climate warming driven fluctuations
in plant species richness compared to the nival belt. To test this hypothesis, 12 summits within this range were investigated
in the canton of Grisons, Switzerland in 2004. Complete lists of vascular plant species consisting of 5–70 species were collected
on each summit and the elevation of the uppermost occurrence of each species was recorded. These data were compared to historical
records over 120 years in age. Within this time, vascular plant species richness increased by 11% per decade on summits in
the alpine-nival ecotone. Despite this considerable change, a comparison with nival summits did not support the hypothesis
that species richness increase at the alpine-nival ecotone is higher than in the nival belt. A general trend of upward migration
in the range of several metres per decade could be observed. Anemochorous species were more often found to be migrating than
zoochorous or autochorous species and migration was higher on calcareous than on siliceous bedrock. A comparison between the
summits with the adjacent slopes in our study revealed that changes in species number could be used as an indicator for climate-induced
changes—if at all—only for the narrow summit areas. |
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Keywords: | Alpine-nival ecotone Climate change Functional species groups Migration rates Species richness change Switzerland |
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