Vegetation dynamics in a fishpond littoral related to human impact

To determine how fishpond vegetation reflects human activities, changes of littoral vegetation of the Opatovický fishpond (South Bohemia) were studied over a period of 26 years. The littoral vegetation of this fishpond has been mapped in 1992 and 1997, and compared with a former study in 1971 together with relation to the soil chemistry of the bottom sediments. The following factors influence the vegetation dynamics: fluctuations of water level, trophic level of habitat, changes in management (mowing) and mechanical disturbances (scraping). The expansion of reed stands (Phragmites australis), disappearance of small sedge stands and a decrease in the area of Glyceria maxima stands were the main characteristics of the vegetation dynamics within the period studied; most other plant communities remained stable. In addition, successional development on scraped shores led to the re-establishment of wetland communities (positive effect) or to ruderal vegetation on islands of deposited material (negative effect). The fishpond may be characterized as meso- to slightly eutrophic and was found to be relatively resistant to the influence of local sources of pollution: the total trophic level (total N, nitrates, phosphates) did not increase at all. As the fishpond has been proposed as a nature reserve for valuable plant communities and water bird diversity, fishery management and human activities in the surrounding area need to be controlled.