Abstract
Assessment of key environmental factors that influence vegetation distribution and formation of plant communities is one of the most important challenges in modern phytocenology. Nowadays, several bioindication systems are applied to determine ecological specificity of plant communities and to establish the leading factors for their environmental differentiation. The system most widely used in Europe, that of H. Ellenberg, contains a numerical score on 6 ecological factors. On the example of vegetation of the valley of the Liman Kuyalnik, Y. Didukh developed the synphytoindication method based on evaluation of phytocenoses with respect to 12 ecological factors: 7 edaphic factors and 5 climatic factors; the method determines a more accurate and complete presentation of the analysis. In the valley of the Liman Kuyalnik (Odesa Oblast) the largest area is covered with halophytic and steppe vegetation. Halophytic vegetation (Therosalicornietea, Festuco-Puccinellietea classes, Juncetea maritimi, Bolboschoenetea maritimi) predominated in the shoreline areas of the valley, whereas steppe (Festuco-Brometea) and petrophytic (Sedo-Scleranthetea) vegetation dominated on the slope sites. With the application of DCA-ordination and synphytoindication methods it was established that distribution of plant communities in the hyper-space of the environmental conditions was most strongly correlated with edaphic factors, whereas microclimatic (light intensity) and climatic (thermo-regime) conditions had somewhat less influence on their differentiation. Water regime and level of soil salinity served as key factors for syntaxa of halophytic vegetation; moisture variability and salt regime, as well as soil moisture and carbonate content were key factors for the steppe vegetation, and thermo-regime was the main factor for petrophytic-steppe and petrophytic vegetation. The "eco-spaces" of these groups largely overlap. Halophytic cenoses are characterized by quite wide ecological ranges by most ecological factors. Steppe communities show much less ecological diversity. In the valley of the liman, all the steppe communities were characterized by stenotopicity in relation to most ecological factors; these factors complexly determine the specificity and diversity of biotopes within the valley, which are unique and require protection and the taking of appropriate measures, depending on the changes in activity of one or another limiting factor. Nowadays, the valley of the Liman Kuyalnik is in a state of environmental disaster. The established relationships in ecological differentiation of plant communities will be applied to further monitoring of biodiversity state, preservation and possible restoration of vegetation types that were native for this unique territory.
Highlights
Within the Kuyalnik Estuary valley they occupy a transitional position between saline-marsh vegetation of Bolboschoenetea maritimi class and saline-steppe vegetation of Festuco-Puccinellietea class
Temperature regime was the key factor for communities of Potentillo arenariae-Linion czernjajevii and Alysso-Sedion unions
The analysis showed that distribution of plant communities most closely correlated with edaphic factors; microclimatic and climatic factors have somewhat less effect on their differentiation, which is consistent with phytosociological studies of other authors (Tölgyesi et al, 2014; Li et al, 2017; Czortek et al, 2018)
Summary
Vegetation cover serves as an indicator of ecosystem state because it responds quickly the changes in environmental conditions (Burger, 2006; Parmar et al, 2016; Lykholat et al, 2018a); it gives the opportunity to make an environmental assessment of a certain territory using phytoindication scales (LaPaix et al, 2009; Ivanova & Zolotova, 2015) and to conduct phytomonitoring of the territory (Klimo et al, 2011; Lykholat et al, 2018b; Jetz et al, 2019; Lashchinskiy et al, 2019). Its effectiveness lies in the possibility of obtaining the required information without direct measurements,of covering all the diversity of syntaxa and reflecting their cumulative effect over a long period of time. Such surveys are undertaken for more comprehensive comparative assessment analysis of some types of plant communities in relation to others, which is important for understanding their place in the system of vegetation cover of certain landscapes or regions (Didukh & Kuzemko, 2014; Pinto et al, 2016). Didukh allow one to conduct a more detailed analysis on 12 ecological factors
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