Vegetation dynamics on exposed pond bottoms in the Ceskobudejovicka basin (Czech Republic)
umberová, Kateřina; Horáková, Viera; Lososová, Zdeňka
The vegetation dynamics on the exposed bottoms of fishponds and storage ponds in the Ceskobudejovická basin (South Bohemia, Czech Republic) were studied. In 2001 2002, a total of 42 permanent plots in 19 storage ponds and 7 plots in 2 nursery fishponds were established. Phytosociological relevés were recorded using the Braun-Blanquet method and stored in the Czech National Phytosociological Database in TURBO(VEG). 445 relevés from autumn 2001 and the vegetation period of 2002 were analysed using the DCA and CCA methods from the package CANOCO, STATISTICA software and JUICE 6.1 software. Species lists exported from TURBO(VEG) served as a general description of species richness. This study attempts to explain the relationship of vegetation cover and floristic spectrum on the one hand to abiotic factors and management on the other hand. The CCA analysis detected moisture and the week in which the data were recorded to be the most important variables. These factors influence the basic vegetation structure and species composition; however, they explain only 2.5% of the variability. Both factors are partly given by the type of summer drying of the pond, i.e., by the management. According to the type of summer drying and vegetation phase we distinguished spring ponds (the storage ponds and nursery fishponds) and summer ponds. The nursery fishponds are only shortly dried in AprilJune. Therefore, annual species with extremely short live cycles occur there, e.g., Coleanthus subtilis. Thermophilous species, germinating in May and June, and plants with longer life cycles are eliminated. The spring storage ponds are dried from December or early spring throughout the whole vegetation period. They are characterized by many perennial species, e.g., Juncus articulatus and Equisetum palustre. In the summer storage ponds, dry mostly for 24 months in summer and early autumn, thermophilous annual species, such as Lindernia dubia, are found.Besides summer drying, other management practices are used in the storage ponds, e.g., herbicide spraying, mowing, liming, etc. These practices can exclude some species from the total species spectrum and can have positive influence on the development of other species. For example herbicides and mowing reduce total cover and competition from some perennial species, which supports the survival of annuals in the vegetation. The diversity of the storage ponds' environments was considerably higher than that of the fishponds, and this was reflected in the species richness. In 17 relevés from fishponds, a total of 24 plant species were found; in 17 comparable relevés from storage ponds, 64 species were recorded.