ALKALINE FENS

Alkaline fens are some of the most valuable and ecologically interesting, at the same time being most difficult to protect European ecosystems. Their functioning is determined by co-existence of external factors such as appropriate geological conditions related with the presence of rocks and minerals of appropriate chemical composition or appropriate functioning of the regional hydrological system, as well as internal ecological mechanisms. The specificity and possibility of habitat survival is mainly determined by its limited fertility, related with high content of ions of some metals, in particular calcium. Well-preserved fragments of such ecosystems are the place of living for extremely high number of endangered and protected species of flora (including so-called “glacial relics”) and fauna, in particular the species from Appendix II of the Habitats Directive, e.g. Saxifraga hirculus, Liparis Loeseli, Hamatocaulis vernicosus, Meesia longiseta, Vertigo moulinsiana and Vertigo angustior.

In European conditions, as well as the areas included in the project, located in the northern Poland, alkaline wetlands are at the borderline of fully natural systems, functioning in a completely autonomous manner and semi-natural ecosystems, owing their form to many centuries of traditional farm cultivation (sporadic mowing with the purpose of biomass for litter for farm animals or occasional grazing). Extensive meadow management for many years facilitated maintenance of alkaline fens in the natural landscape.

It was in the second half of the 20th century, when the intensive drainage of wetlands conducted in Poland in order to intensify farm production led to vanishing of app. 80% of alkaline fens, distinctive of their unique plants. The process of vanishing alkaline fens is continued at present due to long-term effects of hydrological changes in the scale of landscape (common decrease of ground water level). Fens with disrupted water management are subject to drying, eutrophication (due to decomposition of superficial layer of peat), and consequently to accelerated growth of forest and shrub plants. In the past, the tree expansion process was halted by means of meadow and pasture management, whereas currently (due to low quality and value of biomass) alkaline fens are generally outside the scope of farmers’ interest.

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