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

Abstract

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.