Salt marshes determined by ascending brine in northern Poland: land-use changes and vegetation-environment relations
Bosiacka, Beata; Podlasinski, Marek; Pienkowski, Paweł
Most of the European salt and brackish marshes are linked to sea water ingression. Inland salt marshes supplied with saline subterranean waters are more uncommon. In Poland due to the natural factors limiting the development of coastal salt marshes, they are dispersed and cover a surface comparable to inland saline habitats. Two halophilous vegetation sites located at the coastal zone but determined mainly by ascension of relic Mesozoic saline waters have a unique status. The aim of the study was to provide a characteristic of these sites including land-use changes during 1925-2005, physicochemical soil and ground water properties, relations between habitat conditions and species composition, differentiation and qualities of halophilous vegetation and environmental protection prospects. It was shown that a development of drainage network in the Parsęta Valley and Chrząszczewska Island as well as urban infrastructure affected the first site leading to reduction of the wetlands (mainly salt marshes) by 44% and 29%, respectively. The cessation or reduction of traditional salt grassland-use in 1980s led to further decrease in salt meadow area. Primarily, soil and ground water salinity (almost four times higher than in the local Baltic Sea water) determined species and habitat differentiation. Salicornia europaea colonising muds - the only natural sites of this particular habitat in Poland - were linked to the most saline and wet soils. Phytocoenoses of Puccinellia distans-Spergularia marina community were linked to less saline but comparably muddy soils. Less wet and even less saline soils supported phytocoenoses with a significant contribution of Juncus gerardi and patches of Phragmites australis-Atriplex hastata var. salina community and Scirpus maritimus community spreading because of the mowing and grazing abandonment. Salt grassland-use cessation and planned architectural and technical investments call for an urgent implementation of agro-environmental programmes and nature compensation projects to protect these unique sites in northern Poland.