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Nature Park Kopački Rit is situated in eastern Croatia, northwest of the confluence of the Drava and the Danube, and it is one of the largest and most important fluvial-wetland areas in Europe. It was founded in 1973 as an Ornithological Reserve and in 1993 designated as Natural Park comprising the surface of 177 km2. According to the „flood pulse concept“ flood areas are defined as aquatic/terrestrial transit zones where flood dynamic is the main factor shaping habitats and communities. In order to study diversity, composition and conditionality of macrophyte communities we have conducted research during three years on 15 preselected localities with different flood regimes. Regarding the vegetation, the researched localities can be divided into two groups, those with very lush macrophytic vegetation and those without or with very scarce vegetation, where the absence of direct influence of the flood waters of the Danube is the main factor enabling development of the macrophytic vegetation. The vegetation is developed in the area inside the main dam, in very slow flowing or almost stagnant waters with moderate water level fluctuations where several ecological gradients shaping macrophyte communities can be recognized. According to current phytosociological system, the vegetation belongs to three classes, each represented with several orders and alliances: (a) free-floating communities of the class Lemnetea (b) rooted floating or submerged macrophytes from the class Potametea, and (c) the reed vegetation of the class Phragmito-Magnocaricetea. However, in the field, due to the complexity of stands is almost impossible to divide the vegetation in discrete and hierarchically ordered units. Currently favorited splitter approach in describing macrophyte syntaxa is not applicable in the areas with high diversity and complexity of such vegetation. Considering occupied surfaces and populations sizes, Kopački rit is the largest and richest area in Croatia with macrophyte vegetation of shallow, eutrophic, slow flowing or stagnant waters. However, serve droughts in last years have negative influence on these habitats and its vegetation. |
