Assessment of the Dynamics of Plant Communities in the East of the Volga River Delta (1980–2023)

Abstract

The results of a survey of vegetation dynamics on fixed transects in the east of the Volga River delta are presented. Sample plots of 2 × 2 m were laid in ecotopes mainly affected by floods. They underwent inundation or a groundwater level rise during high water periods. Geobotanical relevés of 498 sample plots were compared based on the survey results of 1980, 2011, and 2013. Five groups of plant communities were identified by cluster analysis. DCA ordination was used in combination with the L.G. Ramensky’s indicator values to identify the direction of vegetation succession. It was revealed that most of the vegetation changes on the transects occurred between 1980 and 2011. Reed (Phragmites altissimus (Benth.) Nabille) and cattail (Typha angustifolia L.) thickets replaced forb marsh–meadow phytocenoses. The areas of halophytic phytocenoses sharply decreased: they were replaced by these thickets and meadow communities dominated by Elymus repens (L.) Gould. The authors consider that there are two main reasons for these phenomena. First, this is the increase in the water flow of the Volga River after 1980. Second is the end of hay harvesting on a significant part of meadow wetlands. Changes in the vegetation between 2011 and 2023 were noticeable only on the lower parts of the slopes of the Baer hills. The number of sample plots with communities of the middle-steppe humidification increased here during the last year. These moved down the slopes of the Baer hills, which could be related to changes in climatic parameters towards aridization in 2014–2022 and to a decrease in the flood height by 23 cm.