The weed communities have changed dramatically in the 20th century. Because no weed vegetation relevés were recorded for South Moravia early in this century, changes in potential distribution of the most endangered vegetation type, the association Caucalido daucoidis-Conringietum orientalis, are evaluated using records of its diagnostic species. The diagnostic species group of this association was specified by the statistical calculation of fidelity. It includes Scandix pecten-veneris, Caucalis platycarpos, Bupleurum rotundifolium, Thymelaea passerina, Nigella arvensis, and Ajuga chamaepitys. The coincidence distribution maps of these diagnostic species were prepared. The resulting maps show that the potential distribution of Caucalido-Conringietum is the South Moravian region of thermophilous flora and possibly the adjacent regions of mesophilous flora. The incidence of this plant association in the area declined remarkably in the second half of the 20th century, but in the 1990s its diagnostic species appeared again at several sites.
Species composition, structure and ecological characteristics of the vegetation of two pond types with different management, fishponds and storage ponds, in the Českobudějovická pánev basin (South Bohemia), were compared. A selection of 99 relevés from fishponds and 99 from storage ponds (small ponds used for the storage of marketable fish) made in 2000–2004 were analysed using direct and indirect ordination and ANOVA. The difference between storage ponds and fishponds was found to be more important than gradients correlated with temporal changes, soil moisture and mud depth. Storage ponds had a significantly higher mean number of species, bryophytes, archaeophytes and neophytes and beta-diversity. There were no significant differences in cover values, except of moss layer, which had significantly higher cover in storage ponds. Fishponds had significantly higher mean Ellenberg indicator values for light, continentality, moisture and nutrients. Oenanthe aquatica and Rumex maritimus are typical fishpond species and Amblystegium humile and Eleocharis palustris agg. typical storage pond species. The management of storage ponds is more varied and of different intensity than that of fishponds. It is assumed that management is a crucial factor determining the species richness and influencing the vegetation of these two habitats.
A phytosociological synthesis of weed vegetation of southern Moravia (Czech Republic) was performed using the Braun-Blanquet approach. Gradsect sampling, i.e. a priori stratified selection of sampling sites, was used for the field survey. Using this method, 115 quadrants of the Central European mapping grid (6 × 5.6 km) were chosen. Three hundred and ten relevés recorded in 1997–2002 were classified, based on the Cocktail method, which defines sociological species groups and then creates formal definitions of vegetation units. In total, nine associations of the class Stellarietea mediae were distinguished in southern Moravia. Three associations were included in the alliance Caucalidion lappulae (Lathyro-Adonidetum, Euphorbio-Melandrietum, Veronicetum hederifoliotriphylli) and three in the alliance Scleranthion annui (Aphano-Matricarietum, SperguloScleranthetum, Erophilo-Arabidopsietum). For each of the alliances Veronico-Euphorbion, Spergulo-Oxalidion and Panico-Setarion one association was distinguished, respectively, SetarioFumarietum, Panico-Chenopodietum polyspermi and Echinochloo-Setarietum pumilae . Species composition of these associations is documented in a synoptic table. Their structure, ecology, and distribution are commented.