Impacts of human activities on floating mires of Malom pond at Veresegyház, Hungary

Abstract

The aim of the study is to show the change of the vegetation of floating mires of Malom pond as a result of human impacts. The extensive eutrophication of pond water caused the degradation of vegetation during the 20th century. An increase in the number of algae (Microcystis spp., Cladophora sp., etc.) and a rise in the percentage of nitrogen indicator plants of fertilised soils (Solidago gigantea Ait., Bidens tripartita L., etc.), the disappearance of species indicating nitrogen poor habitats (Menyanthes trifoliata L., Pedicularis palustrisL., etc.) and the extinction of reed-grass vegetation (Utricularia bremii Heer, Ranunculus circinatus Sibth., Potamogeton lucens L., etc.) are all the result of the eutrophication process. Expansion of reeds into the sedgy floating mires and the destruction of reed (in the most pressured areas) are the further proofs. In the second half of the 20th century new artificial fishing-lakes were created in the watershed basin of Malom pond accompanied by the removal of reeds, floating mires, reed-grass vegetation and peat, through dredging. In addition to fishing, the main sources of water pollution were cesspits and the agricultural fertilisers. The elevated eutrophication of the water of Malom pond is attributed to human intervention and the resulting stresses of the system.