Syntaxonomy and ecological differentiation of the pioneer vegetation of Ukraine Classes: Isoëto-Nanojuncetea, Bidentetea

The studies of the pioneer vegetation of freshwater shorelines of water bodies are of particular interest owing to the specific ecology of these habitats and the short cycle for their development in which periods of flooding and subsequent drainage alternate. Using the methods of phytosociological classification and cluster analysis based on the interpretation of 414 phytosociological relevés, the syntaxonomic structure of the pioneer vegetation of freshwater shorelines of the water bodies of Ukraine has been established that are represented by the phytosociological classes Isoëto-Nanojuncetea and Bidentetea. The class Isoëto-Nanojuncetea includes 8 associations that belong to 2 alliances and 1 order and the class Bidentetea includes 10 associations belonging to 2 alliances and 1 order. Phytocoenoses of both classes are more typical for the Polissia region and the forest-steppe zone of Ukraine, where there are favourable habitats with a flat relief, low degree of dissection and a high level of soil humidity. Using a DCA ordination analysis of associations their position in ecological space was determined. It was established that the main factors of ecological differentiation for Isoëto-Nanojuncetea habitats are soil humidity, soil aeration, nitrogen content, as well as temperature regime. Differentiation in the hyperspace of abiotic factors of the class Bidentetea occurs mainly along the gradients of soil humidity, salt regime and acidity. The ecological distribution of syntaxa of this class is also significantly influenced by the concentration of mineral nitrogen compounds in the soil.

Syntaxonomy and ecological differentiation of the pioneer vegetation of Ukraine. 1. Classes: Cakiletea maritimae, Ammophiletea, Crithmo-Staticetea, Crypsietea aculeatae, Therosalicornietea

Pioneer plant communities grow on newly-formed ecotopes of coastal and partially continental areas, on patches that have dried after the surface water flooding. They are affected by sea tides, wind-induced effect, salinity, denudation, accumulation and sharp changes in soil humidity. To these factors are added chemical and biological pollution, as well as anthropogenic pressure. Due to these reasons, such plant communities have a specific floristic composition, structure, functional regime and resilience mechanisms, which are different from coenoses of more stable habitats. On the basis of the analysis of more than 600 phytosociological relevés using TWINSPAN modified algorithm the current state of littoral and halophytic classes of pioneer vegetation in Ukraine has been established and their syntaxonomic structure identified. It has been determined that the level of pioneer phytocoenoses diversity in Ukraine is similar to that of Central Europe. The Cakiletea maritimae class is presented by 1 order, 1 alliance, and 4 associations; Ammophiletea – by 1 order, 1 alliance, and 8 associations; Crithmo-Staticetea – by 1 order, 2 alliances, and 3 associations; Crypsietea aculeatae – by 1 order, 3 alliances, and 4 associations, Therosalicornietea – by 1 order, 2 alliances, and 10 associations. Synoptic tables of vegetation classes are given and nine alliances are briefly characterized. Using DCA-ordination analysis of syntaxa in the association-rank level we identified that the main factors of ecological differentiation are soil humidity and aeration as well as the nitrogen content. For the pioneer plant communities, other significant impact factors are the extremality of environmental conditions, their unevenness and non-equilibrium, in particular, the mechanical action of the sea waves, the dynamic processes of denudation and accumulation, salinity, as well as the variability of damping during the year. This research contributes to the identification of the place of the distinguished syntaxa of Ukrainian pioneer vegetation in the European system.

Distribution and habitat preferences of Polygonum arenarium subsp. arenarium (Polygonaceae) in Slovakia

The paper presents data on the distribution and habitat preferences of Polygonum arenarium subsp. arenarium in Slovakia. The study showed a rapid decrease in the number of localities in Slovakia in recent decades, due to destruction of sandy habitats. At present the taxon is considered to be very rare. We recorded it in stands of pioneer vegetation of the Festucetea vaginatae class developed on open sandy dunes, in the associations Festucetum vaginatae and Bassio laniflorae-Brometum tectorum.