Spatio-temporal differentiation of distribution patterns of Salicornia perennans, Halimione verrucifera, and Suaeda cf. prostrata (Chenopodiaceae) in the plain part of Ukraine during the Allerød–Holocene

Abstract

The article provides paleofloristic evidence for the history of formation of modern halophytic vegetation in the plain part of Ukraine. Pollen grains of representatives of selected taxa of the family Chenopodiaceae, which belong to the ecological group of halophytes, are important components of palynological characteristics of the PleistoceneHolocene deposits. Results of species-level identifications of halophyte fossil pollen provide a solid basis for the reconstruction of distribution patterns of plant communities on saline soils in space and time. Our analysis of paleofloristic data included both the original results of species-level identifications of pollen grains of Chenopodiaceae and the relevant literature data. The objective of the present research was to analyze and generalize the results of paleofloristic studies that provide evidence on the participation of three characteristic species (Salicornia perennans, Halimione verrucifera, and Suaeda cf. prostrata) in the palynofloras of the Allerod– Holocene deposits of the Right-Bank and Left-Bank parts of the Forest, Forest-Steppe, and Steppe physiographic and vegetation zones of Ukraine. The selected model species at present predominantly occur on wet solonchaks within the present-day Steppe Zone of Ukraine. Only occasionally they occur in the southern parts of the Left-Bank area of the Forest-Steppe Zone. It is worth noting that S. perennans, H. verrucifera and S. cf. prostrata can be also considered as indicators of changes of soil conditions in the past. To increase the reliability of specific-level identifications of fossil pollen of these model taxa, additional palynomorphological studies using both light microscopy and scanning electronic microscopy were performed. The generalized results of paleofloristic studies (fossil palynofloras in deposits of 12 sections) allowed tracing the spatiotemporal differentiation of distribution patterns of S. perennans, H. verrucifera, and S. cf. prostrata in the plain part of Ukraine during the Allerod–Holocene. We first reconstructed both a history of the dynamic ranges (areas of distribution/occurrence) of each of these three indicator species of halophytic vegetation and paleofloristic evidence of distribution of saline soils (in particular, wet salt meadows, salt marshes) in the plain part of Ukraine in space and time forthe considered period. It is worth emphasizing that, as compared to the Right-Bank area, paleofloristic materials presently available demonstrate that the processes of soil salinization were more common in the territory of the Left Bank of the Forest and Forest-Steppe zones of Ukraine during the Late (Younger) Dryas. This trend is also quite clearly traced in the Holocene. Salicornia perennans, H. verrucifera, and Suaeda cf. prostrata most often participated in the formation of plant communities common in saline soils during the Early (PB, BO) and Middle (SB) Holocene in the Left-Bank area of the Forest-Steppe Zone. Due to the results of palynomorphological studies, additional qualitative and quantitative diagnostic characters have been identified and summarized; these characters can be used in the future for species-level identification of pollen grains of S. perennans, H. verrucifera, and S. cf. prostrata in the spore-pollen analysis of deposits of the Quaternary of Northern Eurasia.