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Water contraction drives stronger the formation of diatom assemblages in stream than human induced microhabitat-variability
211-228Views:235Today, climate change, together with other anthropogenic influences is considered as a major threat affecting aquatic ecosystems in several ways. Here, altering water contraction (standing and flowing phases) and human-induced habitat variability (natural and artificial stream sections) were studied as modifying factors driving community changes in benthic diatom assemblages of a Hungarian small lowland stream (Létai-ér). We assumed notable compositional differences between phases and habitats, but we expected these differences to decrease with drying. Moreover, lower diversity was hypothesized in assemblages of both artificial section and flowing phase. While taxonomic composition did not reveal significant differences between the sections, well pronounced compositional changes were found between phases. Surprisingly, no significant diversity changes were observed during water contraction. Compared to the natural microhabitat, however, artificial stream section was found to maintain more diverse diatom community. These results emphasize that modification effects of climate change induced hydrological extremes can lead to remarkable compositional changes in benthic algal assemblages even on a short time scale, that must be taken into account in both water management and nature conservation strategies.
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Fern (Pteridopsida) flora of South Nyírség (East Hungary)
162–182Views:381The study presents a number of new data on the fern flora of South Nyírség, and reviews all available literature and herbarium fern records from the area. A total of 19 Pteridopsida species were detected in the region. The hart's tongue fern (Asplenium scolopendrium) and the soft shield fern (Polystichum setiferum) were hitherto unknown in the whole Nyírség region (flora district “Nyírségense”). The broad buckler-fern (Dryopteris dilatata), scaly male fern (Dryopteris affinis) and floating fern (Salvinia natans) are new records to the area of South Nyírség. Dryopteris dilatata has been found in a surprisingly great number of localities. Some morphological characters facilitating identification of this species are also discussed. The local pine plantations, fens, carrs and humid deciduous forests are important habitats for ferns. In some localities the co-occurrence of 5-6 fern species were observed. The increasing aridity in the last decade is posing a serious threat to ferns in the area.
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Data on the pioneer vegetation of the Lake Velence
203–208Views:235Lake Velence is one of Hungary's largest saline lakes. Part of its natural dynamics is that certain parts of the lake bed regularly dry out, providing pioneer surfaces suitable for the emergence of plants of the mudflats and drying (saline) ponds. During the particularly dry year of 2022, the water level was permanently and significantly low, allowing to study the vegetation of the dry lake bed. In the first half of the last century, the natural vegetation of the lakeshore (including salt steppes) was studied, but there are very few records of the pioneer species of the lake bed. The salt steppes around the lake have now largely declined, but due to low water levels, some of their characteristic species are still present in the lake bed (though, usually in low number of individuals). Examples include Crypsis aculeata, Cyperus pannonicus, Suaeda pannonica, the once abundant Suaeda prostrata, and the previously rare Crypsis schoenoides and Spergularia salina. Spergularia maritima was once widespread but currently not found in the lake bed. Although, Schoenoplectus litoralis is not a member of the ephemeral vegetation, but is a characteristic plant of the littoral zone of Lake Velence. This species probably appeared therein the middle of the last century and is currently spreading.