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EN
The paper presents results of the studies conducted to determine causes and directions of transformations in vegetation of meadow-pasture communities in the area of the Wielki Łęg Obrzański [Great Obra Floodmeadows]. Multifaceted natural and habitat analyses were conducted on over 1800 relevés prepared in the vegetation seasons of 2005–2009 according to Braun-Blanquet. On their basis the phytosociological and floristic structure was analysed and habitat conditions were determined by phytoindication. Moreover, laboratory methods were applied in soil analyses to determine contents of basic macro- and microelements and groundwater table levels were recorded. Results referred to the documentation and archive literature made it possible to determine causes of transformations in plant communities in that area and outline probable directions in which succession was progressing. A lack of regular land use patterns is seen as the primary cause for the transformation in the flora of the Wielki Łęg Obrzański, particularly in the last 20 years. A considerable limitation of land use in certain sections of this area has led to the initiation of dominance of nitrophilic species such as Urtica dioica, Cirsium arvense, Potentilla anserina or Galium mollugo, while in the thinned sward it led to the development of grass species with very limited economic importance. Another equally important factor affecting the structure of vegetation cover is connected with air and water relations in soils, determined by the drainage system operating there for the last 200 years and by precipitation.
XX
The paper presents the results of the research on the speed and level of colonization of the unexploited railway lines by grasses. Railways tracks are an inseparable element of the human-shaped environments. These areas have specific ecological-edafical conditions and only plants of wide ecological amplitude are able to get control over them. Among grasses there is a significant number of species whose biological properties, resistance to environmental stresses and ability to survive in extreme conditions let them overrun and turf difficult terrains. These are mostly species which root deeply, creep, form a large number of diasporas and are often connected with significantly drying habitats, such as Arrhenatherum elatius, Dactylis glomerata, Festuca ovina, Festuca rubra and Poa pratensis, which grow relatively fast within peatlands. The expansion of grasses typical to ecosystems crossed by railway tracks were also identified in these areas e.g. Melica nutans, Poa nemoralis in forestry areas, Phragmites australis, Bromus inermis on wetlands and Apera spica-venti, Bromus secalinus, Echinochloa crus-galli or Setaria viridis on agricultural terrains. However, these taxons appeared usually single with a minor share. Total number of grasses was 31.
PL
W dolinie Środkowej Mogilnicy oceniano walory przyrodnicze zbiorowisk łąkowych na podstawie liczby gatunków, wskaźnika różnorodności florystycznej Shannona-Wienera (H’) i metody waloryzacji Oświta oraz ich wartość gospodarczą i użytkową (LWU). Określono ponadto warunki siedliskowe wyróżnionych zbiorowisk: uwilgotnienie (F), odczyn gleby (R) oraz jej zasobność w azot (N), z zastosowaniem liczb wskaźnikowych Ellenberga. Walory przyrodnicze i użytkowe wyróżnionych zbiorowisk zależą od usytuowania w dolinie. Zbiorowiska położone najbliżej rzeki, zaklasyfikowane do klasy Phragmitetea, wykształcone są w formie typowej i przedstawiają duże oraz umiarkowanie duże walory przyrodnicze (od V do VII klasy waloryzacji), jednakże ich ruń ma najczęściej niską wartość użytkową (LWU od 1,63 do 6,90). Aktualnie użytkowane zbiorowiska klasy Molinio-Arrhenatheretea przedstawiają umiarkowane walory przyrodnicze (III i IV klasa waloryzacji). Z łąk tych uzyskuje się wysokie plony I pokosu (4,4 do 5,7 t s.m.· ha-1) o dobrej wartości użytkowej (LWU od 7,37 do 7,56).
EN
Natural importance and economical and usefulness values (FVS) of meadows situated in the valley of the central Mogilnica River were assessed. The natural value was determined on the basis of: the number of species in a phytosociological relevés, phytosociological structure, floristic diversity expressed by the Shannon-Wiener index (H’) and the method of plant community valorization according to Oświt. Site conditions: moisture (F), soil reaction (R), soil nitrogen content (N) of the examined meadow communities were evaluated using the Ellenberg phyto-indication. Both natural and usefulness values of the examined communities depend on the place of occurrence in the valley. The communities situated closest to the river, which were assigned to the class of Phragmitetea, developed in their typical forms and presented significant and moderately significant natural values, although their sward was found to be characterized by low usefulness value. Communities growing further from the river, representing the Molinio-Arrhena-theretea class, are utilized at the present time. Grasses found in these communities are of moderate natural importance but the meadows provide high yields of good fodder value.
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