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The aim of our investigations conducted on grasslands situated in the region of Wielkopolska was to analyze changes in the occurrence of selected plant species in the sward of meadow communities, to determine causes of their expansion and the impact on natural and useful values of these plant complexes. The occurrence of Deschampsia caespitosa, Holcus lanatus and Cirsium arvense from meadow communities was subject to comparative analysis. The behaviour of the above species, described as aggressive, was analyzed on the basis of changes in the frequency of their occurrence (i.e. constancy degree) in communities and the achieved ground covering coefficient. In addition, causes and consequences of the expansive behaviour of the analyzed plant species were assessed. The expansive behaviour of Deschampsia caespitosa, Holcus lanatus and Cirsium arvense is associated, on the one hand, with the occupation of new sites and, on the other, with a significant increase in the proportion of these species in the sward as evidenced by the obtained values of the ground-covering coefficient. The spreading the analyzed plant species results from the direct or indirect anthropo-pressure on sites and vegetation type of meadow communities. The discussed expansive species – course hairgrass, velvet grass and Canadian thistle – occurring in grass communities, especially during longer time intervals, exert unfavourable influence on their natural and use values.
Anthropopressure directly and indirectly affects changes in species composition in plant communities, including communities of Phalaridetum arundinaceae. Variations in habitat conditions, especially moisture content, contribute to the disappearance of typical rush associations and lead to the development of lower phytosociological units. The natural value of Phalaridetum arundinaceae syntaxons is affected by the relative share of synanthropic species. Their occurrence is determined by habitat conditions and land use.
Przeprowadzono badania (ankietowe) aktywności przedsiębiorstw w rozwoju produktów w wybranych branżach przemysłu spożywczego. Wyniki badań wskazują na ograniczoną skuteczność postępowania rozwojowego oraz na konieczność jego doskonalenia w celu zwiększenia konkurencyjności przedsiębiorstw przetwórczych.
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.
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