The Balkan wet grassland vegetation: a prerequisite to better understanding of European habitat diversity |
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Authors: | Michal Hájek Petra Hájková Desislava Sopotlieva Iva Apostolova Nikolay Velev |
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Institution: | (1) Institute of Botany, Czech Academy of Sciences, 3b Poříćí, 60300 Brno, Czech Republic;(2) Institute of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic;(3) Institute of Botany, Bulgarian Academy of Sciences, Acad. Georgi Bonchev St., bl.23, 1113 Sofia, Bulgaria |
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Abstract: | The knowledge of broad-scale floristic variation in wet grasslands, which are endangered throughout Europe, is still limited
and some regions have remained unexplored so far. In addition, hitherto published phytosociological studies were concentrated
at the national level and therefore national vegetation classifications are not consistent with each other. In order to overcome
these shortcomings of traditional phytosociology, we gathered original data from Bulgaria and analysed them together with
the data from Central Europe. We further analysed major compositional gradients within Bulgarian wet grasslands and changes
in species richness along them. We sampled 164 wet grassland vegetation plots throughout Bulgaria. We further prepared a restricted
data set of wet grasslands from Central-European phytosociological databases. Both data sets were merged and classified by
modified TWINSPAN. Four distinct vegetation types were differentiated. Even if they correspond with traditional alliances,
which are primarily drawn as geographically defined units in Western and Central Europe (sub-Mediterranean Trifolion resupinati, sub-continental Deschampsion cespitosae and Molinion caeruleae and sub-oceanic Calthion palustris), they all occur in Bulgaria. When more precise classification was applied, two types of sub-Mediterranean wet grasslands
and one high-altitude type of Calthion grasslands were detected solely in Bulgaria. DCA analysis showed that altitude is a dominant gradient controlling variation
in Balkan wet grasslands. The second DCA axis was interpreted as the gradient of nutrient availability. Species richness shows
skewed-unimodal trends along both major gradients, with the highest species richness in intermittently wet nutrient-limited
grasslands. Tukey post-hoc test of altitudinal differences amongst vegetation types is significant for all pairs of clusters,
suggesting that altitudinal differentiation is responsible for co-occurrence of nearly all European types of wet grasslands
in Bulgaria. Our results suggest that (1) climate is an important factor for the diversity of wet grasslands; (2) Balkan vegetation
of middle altitudes matches with that of Central Europe, whereas that of the lowest altitudes corresponds rather to the sub-Mediterranean
region and high mountains are specific; (3) upward shift of Central-European vegetation types in southern Europe, so often
described in forest vegetation is also evident for grassland vegetation and (4) the high diversity of Balkan vegetation is
determined by a diverse relief enabling confluence of habitats possessing different climatic conditions. |
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Keywords: | Altitude Climate Compositional data analysis Molinietalia Wet meadows Wetlands |
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