Arcto-Alpine Species at Their Niche Margin: the Western Carpathian Refugia of Juncus castaneus and J. triglumis in Slovakia

Abstract

Juncus castaneus and J. triglumis are umbrella species of moist calcareous tundra and arctic-alpine initial fens (the Caricion atrofusco-saxatilis alliance), considered to be glacial relicts in the central-European Mts. Here we report new findings from the Western Carpathians (Slovakia). We analysed species composition of plant communities with the target Juncus species in a wide geographical context, using 20 available vegetation-plot records from the Carpathians, 711 records from other European regions, and formal definitions of fen alliances taken from a pan-European vegetation synthesis. The first gradient of non-metric multidimensional scaling (NMDS) differentiated alpine and arctic samples. The second principal gradient between Caricion atrofusco-saxatilis and other vegetation types was of similar importance. Records from the Western Carpathians assumed a marginal position in the gradient space, while records from the Eastern Carpathians (Romania) appeared to be similar to those from the Alps. Generally, Carpathian records did not match the formal definition of the Caricion atrofusco-saxatilis alliance. Although the arctic-alpine rush species persist occasionally in spring, fen and tundra microrefugia in the Carpathians, they do not belong in similar plant communities as in the Alps or in the Arctic.