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In years 1969 and 1980-91 geobotanical research was carried out on the area of 200 ha of permanent grasslands situated in the Gopło-Warta Canal depression in the zone of the strongest contamination with industrial gases from the neighbouring aluminium works. The total of 150 phytosociological records were taken with the use of the Braun-Blanquet method. Furthemore, chemical soil and plant analyses as well as the examination of the site were conducted. Meadow plants showed varying concentrations of fluorine ranging from 0.65 to 85.2 mg %, and 95 % of the plant samples were toxic to farm animals. The examined meadows are situated primarily on semihydrogenic and podzolic gley soils. However, there are also places where bog and black soils occur. Soils were mainly acid and slightly acid. Chemical analysis showed that the soils are poor in potassium and phosphorus. During the period of studies unfavourable changes occured in the physico-chemical properties of the site: both soil moisture content and density increased while its oxygenation and porosity declined. Soil reaction was also found to have increased. Economically useful plant communities which used to occupy 37.5 % of the area were reduced considerably and now occupy only 12 % (Arrhenatheretum elatioris and Lolio-Cynosuretum). They were replaced by low value plant communities (Deschampsia caespitosa, Carex fusca, Carex gracilis, Molinia coerulea) which currently occupy 88 % of the area. Furthermore, considerable amounts of meadow weeds and plant semiparasites were also found in the examined meadow swards. The quantities of fluorine in plants showed a declining tendency which may have been due to a decrease in the discharge of fluorine into the atmosphere observed recently. Thus, it can be said that fluorine causes injury to plants and leads to the replacement of more valuable species by species economically less valuable. Moreover, these unfavourable changes are further reinforced by negative site changes caused by incorrect management practices quite common on these contaminated areas.
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