Is the riparian habitat creation an effective measure of plant conservation within the urbanized area?

Abstract

The study presents results of habitat creation and riparian vegetation recovery in artificial oxbow lakes in urbanized area within the large river valley. The investigation of open water, rush and wet meadows flora and vegetation in three ponds located in the city centre of Opole was conducted in years 2001–2013. Oxbow lakes were constructed as a compensation measure and no vegetation was transplanted into the ponds on purpose. 13-years observation showed that (1) the red-listed species are able to spontaneous reoccurrence after habitat restoration, but they can thrive only in first years of oxbow lakes recolonisation process, (2) there are some restoration constraints, especially in relation to Phragmites australis and Nuphar lutea expansion, but alien species invasions were insignificant and (3) the species number and vegetation cover was constantly increasing during the recolonisation process in recreated oxbow lakes. The dynamic of vegetation was considerable, especially in first 6 years of experiment when the significant increase in diversity and richness of native plant species was observed. After that time, the increasing expansion of P. australis and N. lutea was noted causing the decline of several species and vegetation types. So, restoring just the environmental conditions may be sufficient for a limited period of time only. Strong disturbances, much intense that moderate inundations, imitating disastrous flooding within the valley each 10–13 years are need to maintain the ecological niches for river corridor and riparian species.