Tuexenia : Mitteilungen der Floristisch-Soziologischen Arbeitsgemeinschaft, Band 31 (2011)
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- Festuco-Brometea (3)
- Koelerio-Corynephoretea (2)
- Molinio-Arrhenatheretea (2)
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Compared to other grassland types across Slovakia, dry grasslands harbour species-rich and specialised ant communities. High diversity and species richness of ants may be seen as a consequence of (i) the specific structure of dry grassland vegetation, (ii) long-term ecological stability, and (iii) currently low or absent management-induced disturbance. With special regard to dry grasslands, we report on structural characteristics of vegetation and low-disturbance regime, which contribute to ant assemblage structure. Our study was carried out in the Štiavnické Vrchy Mts. (Central Slovakia), a region with a historically well-developed grassland area. We established a set of 25 research plots within southorientated grassland habitats representing five different grassland types: wet managed and wet abandoned grasslands, mesic managed and mesic abandoned grasslands (Arrhenatherion elatioris), and dry abandoned grassland habitats (Asplenio-Festucion glaucae). Each habitat type was represented by five plots. At each plot, a set of ten pitfall traps was used to sample ground-foraging ant assemblages. Around each trap, structural characteristics of vegetation and microhabitat were assessed. Dry grasslands were shown to have a specific microhabitat structure, characterised by the presence of a well-developed moss and lichen layer, exposed bedrock, bare soil, and significantly lower, although species-rich vege - tation. Besides the specific microhabitat structure, the absence of management may have contributed to the distinctiveness of these ant assemblages compared to those associated with other grassland categories. Ant assemblages were more species-rich, and the activity of ants was higher in recently abandoned grassland habitats. The effect of abandonment was quite opposite for plants, whose species-richness was, contrary to ants, higher within managed sites.
Using four exclosures, the impact of mouflon grazing and weather on plant communities of the phytosociological alliances Koelerio-Phleion phleoidis and Hyperico perforati-Scleranthion perennis occurring on shallow soils within a forest landscape was studied in the Křivoklátsko Biosphere Reserve (Czech Republic) during seven years. In the years 2004–2010, the vascular plant species composition was recorded annually on a total of eight fenced and eight control plots, each 2 m × 1 m in size. Treatment, time, and weather data were used as explanatory variables in ordination and correlation analyses. Cover values of different life forms and indicator values varied significantly in dependence on the weather conditions of the preceding five months; however, correlations varied according to the vegetation type and were rather rarely detected. The effect of fencing appeared important in all study plots; however, the temporal trends were significant only in half of them. We did not find a significant interaction between treatment and time in the total dataset. A successional change was detected in one fenced plot only; in all other cases, the species composition fluctuated – a phenomenon that is not directly attributable to weather conditions. In the fenced plots, the herbaceous vegetation cover decreased, mainly due to litter accumulation and partly due to shrub encroachment. At least some parts of the valuable and species-rich habitats could be maintained under high game density, but some parts are endangered by eutrophication and game grazing. Nature conservation management should balance both mechanisms.
Many current approaches to the formal definition of vegetation units have the disadvantage of leaving a large amount of relevés unclassified. In this paper I propose a new method for the unambiguous assignment of relevés, which is based on the summarised cover value of diagnostic species. In the first step, a relevé is assigned to the class with the highest cover score. For this purpose, the character and differential species of the class as well as the character species of all subordinated syntaxa are considered diagnostic. Once the class has been determined, the assignment proceeds successively to the lower ranks. This method, which may be called “summarised percentage cover approach”, uses solely the diagnostic species of syntaxa for the assignment of relevés to vegetation units, making additional formal definitions unnecessary. As a test data set, I used 487 relevés of fringe vegetation and grasslands of nutrient-poor sites sampled in the Vienna Woods (Wienerwald), Austria. All relevés were provisorily classified at alliances level, mostly following the assignment of the original authors. TWINSPAN and DCA were applied to evaluate this preliminary classification. Diagnostic species for both the alliance and the class level were identified using the total cover value ratio as fidelity measure. The subjective classification was largely confirmed by the numerical methods. On basis of the summarised cover of Trifolio-Geranietea and Festuco-Brometea species, between 64% (Geranion sanguinei) and 99% (Seslerio-Festucion pallentis) of the relevés were reassigned to the same class as in the original classification. The fact that a considerable amount of relevés originally classified as Geranion sanguinei was reassigned to grasslands reflects the problems in delimiting fringe communities rather than a poor performance of the assignment method. The “summarised percentage cover approach” allows not only for the unequivocal assignment of relevés to an existing classification system, but may also help to improve classifications by clarifying the delimitation of higher syntaxa.
A long-term systematic survey of grassland communities was performed in the Biele Karpaty Mts. in Slovakia. The main aims of the research were i) syntaxonomical classification of meso- and subxerophilous grassland vegetation, ii) analysis of the main gradients in species composition, iii) evaluation of the effect of environmental factors on species composition of grasslands. The data set included 342 phytosociological relevés of grasslands recorded between 1991 and 1999. For the classification of relevés to associations, the expert system for identification of grassland vegetation of Slovakia was used. The main environmental gradients of species composition were analysed by detrended correspondence analysis (DCA). For the ecological interpretation of ordination axes Ellenberg indicator values were used. The relationship between species composition and environmental factors (geology, pedology, climate, topography, management) was analysed by canonical correspondence analysis (CCA). The expert system identified (according to association definitions) 220 phytosociological relevés (64% of the whole data set). Grassland communities were classified within seven associations belonging to four alliances and three classes: Festuco-Brometea: Bromion erecti and Cirsio-Brachypodion pinnati; Molinio- Arrhenatheretea: Arrhenatherion; Nardetea strictae: Violion caninae. The results of the DCA support our assumption that the main environmental gradient in species compositions of grasslands is related to moisture and soil reaction (content of CaCO3 in the soil). The results of the direct gradient analysis (CCA) show that all 23 environmental variables explained 16.15% of the variability of the species data. The most important factors affecting the data variation were precipitation and geological bedrock.
We first report from the 7th European Dry Grassland Meeting held 27 May to 1 June 2010 in Smolenice, Slovakia, devoted to the main topic "Succession, restoration and management of dry grasslands". Apart from the scientific programme and the excursions, we also summarise the outcomes of the General Assembly of the EDGG and present the Smolenice Grassland Declaration. Then we take stock of the dynamic development of the European Dry Grassland Group (EDGG), report on its activities during the past year, and announce its future plans. Finally, we give a short introduction to the four articles of this Special Feature, which deal with biodiversity patterns, vegetation classification, and dynamics of dry grassland habitats. One presents a detailed phytosociological study of the xeric and mesic grasslands of the Slovak part of the Biele Karpaty Mts. The second provides a new numeric approach to the assignment of relevés to syntaxa and exemplifies this in a case study for the delimitation of the classes Festuco-Brometea against Trifolio-Geranietea sanguinei in Austria. The third article investigates the septennial impact of mouflon grazing and weather on dry grassland plant communities in dry grassland patches of the Czech Republic. The fourth article deals with long-term abandonment of grasslands in Central Slovakia and shows the importance of vegetation structure, ecological stability, and low-disturbance regime for specific ant assemblages.