Nature valuation of plant communities in the Zagorow polder including water content parameters

Geobotanical studies conducted in spring in 2011–2012 in the Zagórów polder washland, covered by the ecological restoration programme, provided assessment of current nature value of plant communities and indicated potential directions of their further transformations as a result of changes in habitat water content levels. Based on the analyses of 77 relevés of 50–100 m2 each, prepared following the Braun-Blanquet method, water levels were assessed by phytoindication using moisture indicator values (F) according to Ellenberg et al. (1992). Moreover, nature value of vegetation was assessed based on the botanical structure, geo-historical spectrum, life form structure as well as the nature valuation index in the 10-point scale according to Oświt (2000). Based on relevés the area was valuated using the point score method according to Mahon & Miller (2003). An attempt was made to indicate potential directions of changes in vegetation, based on the determination of dependencies between certain parameters assessing its current condition and habitat conditions. Habitat water content connected with the supply of water through a network of culverts, geomorphology of the area and land use, affects the distribution of phytocenoses in the polder and their considerable diversity, which was confirmed by the identification of 19 plant communities from six phytosociological classes. Further maintenance of water relations and land use results in the transformation of plant communities: in the vicinity of culverts – towards the class Phragmitetea, in swamps and around small water bodies – towards communities of the classes Salicetea purpurea or Alnetea glutinosae, at longer distances from culverts in leveled and agriculturally utilised areas – towards the orders Trifolio fragiferae-Agrostietalia stoloniferae and Molinietalia, while in areas at valley margins the succession progresses towards communities of the class Nardo-Callunetea.