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The Plitvice Lakes and the Krka River – comparison between the two largest areas with moss dominated tufa forming vegetation in Croatia

This presentation aims to describe and compare moss diversity and vegetation of two large areas with tufa forming vegetation dominated by bryophytes – the Plitvice Lakes (Alpine Biogeographical Region) and the Krka River (Mediterranean Biogeographical Region). The Plitvice lakes are a system of 16 larger and several smaller lakes, separated by tufa barriers, which stretches along 8 km, representing the largest habitat of the tufa forming moss communities (Cratoneurion commutati) in Croatia and the whole of Europe. The Krka River is a large karstic river with tufa barrages forming a complex system of interchanging fast and slow water flow, waterfalls and barrage lakes. Seven waterfall systems harbouring tufa forming bryophyte communities are situated along the 73 km of the river course before the mouth into the Adriatic Sea. Ninety phytosociological relevés were made on the Plitvice Lakes and 52 on the Krka River. They were analyzed using various multivariate techniques (TWINSPAN, DCA), Ellenberg’s ecological indicator values and fidelity indices. Phytosociological affiliation of species and biogeographic elements were also analysed. Moss communities could be assigned partially to the Cratoneurion commutati and partially to the alliance Adiantion Br.Bl. ex Horvatić 1934, but sharing a large proportion of species. Comparison of floristic composition of communities from two the biogeographic regions reveals high resemblance in main species as well as the low proportion of species assigned as characteristic for the class Montio-Cardaminetea Br.-Bl. et Tx. ex Klika et Hadač 1944, where Cratoneurion commutati is placed. Light, moisture (including water velocity) and temperature are the most important environmental factors influencing vegetation difference among these areas. In both areas, considering the eastern limit category, dominant circumpolar species are followed by European ones. Considering major biomes in both areas boreo- temperate and southern-temperate elements are the most prominent. Boreotemperate element has the highest proportion of species followed by southern-temperate element on the Plitvice Lakes, while these proportions are reversed on the Krka River. We can conclude (1) that differences between communities of the two areas are based rather on the quantitative proportion of species than on qualitative differences in species composition, (2) that differences inside communities of a certain area are higher than between areas and (3) that ecological gradients reflected in species composition are similar in both areas.

karst waters, SE Europe, Dinarides, Cratoneurion, Adiantion

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