Changes in floristic richness and diversity of phytocoenoses on riparian habitats affected by diverse land-use forms

In many ecological studies the theory prevails that the increased human economic activity can lead to simplification of species composition of phytocoenoses and a decline of their species diversity. However, there are also other views on this issue. Therefore, an attempt was undertaken to verify these contradictory opinions. The research was conducted at three sites characterised by a diversified and intensified land use form (the nature reserve, 50 year-old poplar plantation and a grassland). The results from the nature reserve were compared with the data for 1963-1965 when other plant communities dominated in the reserve. The results of field observations collected in the form of relevés were used to assess the number of species, α-species diversity of phytocoenoses and ß-diversity.The largest number of species was found in the meadow, a fewer species were recorded in the reserve and the fewest in the poplar plantation; whereas the average number of species per relevé and the differences between the sites were minor. The species heterogeneity index varied within the range of 3.11–3.36, whereas the extreme differences were recorded in the reserve between the current results and the results from the 1960s. The studied phytocoenoses differed mostly in ß-diversity. The average index for the poplar plantation was lower than mean values of indices recorded in communities of the riparian forest and meadows. The obtained results support the opinion about non linear correlation between the increased disturbances and the decline of species richness and species diversity in phytocoenoses