Ecological and phytocenotic statistical analysis of marsh biotopes of the Tylihul-Southern buh interfluve’s rivers

Abstract

Marshes as wetlands in the steppe zone are the most productive natural complexes having high biodiversity and natural biofiltration capabilities are not inferior to forests in the forest-steppe and forest zones.

Excessive anthropogenic pressure on the zone of river floodplains and climate aridization in recent years have become the main negative factors in the transformation of floodplains into fields and pastures. Considering the significant value of floodplains as single natural biocomplexes in the south of Ukraine and the rapid rate of their degradation studies of the latter are very relevant. An analysis of the available publications indicates that despite a detailed study of the delta floodplains of the main river streams of the North-Western Black Sea Region (Dubiny D.V. (2004, 2006, 2007, 2013), Yu.R. Shelyag-Sosonko (2004, 2006), S. Noigoyzlovoi , T.P. Dziuba (2004), B.A. Baranovsky (2005), I.O. Mazur (2017)), the marsh vegetation of medium and small rivers in the south of Ukraine still requires investigation. Accordingly, the aim of this work is the ecological-phytocenotic statistical analysis of the marsh biotopes of the Tiligul-Bug interfluve rivers in the current ecological and hydrological conditions of floodplains.

The materials are based on our own factual material collected during field research of floodplains and flooded vegetation in the territory of the Tiligul-Bug interfluve in the period 2017-2020. The study covered the flooded biotopes of the lower Southern Bug, middle steppe rivers Chichikliya, Tiligule and Kodyma, which is the northern boundary of the interfluve flowing in the forest-steppe zone.

As the main research methods, standard methods of field hydrological, landscape and botanical studies were selected. Statistical analysis was carried out on the basis of the standard Statistics software package of the Exel-2019 operating system.

Modern ecological and hydrological conditions for the existence of marshes are typical for the rivers of the steppe zone of Europe and are characterized by the instability of the hydrological regime of floodplains. Accordingly, the flow and hydration of the hydrotope contributes to the differentiation of flooded biotopes and their vegetation.

The drying up of small rivers due to modern aridization of the south of Ukraine contributes to a significant drying out of the basal soil layer of the floodplains, and as a result, a decrease in bio productivity and grass stand height.

The marshes of the Tiligul-Yuzhny interfluve are represented by biotopes of constant water flowage, biotopes of partial watering and excess humidification; biotopes of sufficient and insufficient humidification with the corresponding types of plant community.

 The most cenotic rich biotopes of excess and sufficient humidification, grown with meadow vegetation. Especially the floristic richness of the latter is concentrated on the floodplains of the Southern Bug with a more or less stable hydrological regime, in comparison with small rivers. The latter is explained by the fact that the meadow vegetation cover is formed by various hydromorph species (hygromesophytes, mesophytes, mesoxerophytes), which are sufficiently plastic and can exist both in conditions of excessive moisture (flood period) and periodic drying of food paths (low-water period). However, the unstable hydrological regime of the floodplains and, as a result, significant fluctuations in the water level on biotopes of constant flow (before drying out) create critical conditions for the existence of typical aquatic vegetation, therefore the diversity of the latter is sharply limited (from about 5 to 15 phytocentric units ). It should also be added that the greater coenotic richness of meadow halophytic vegetation and real salt marsh vegetation is recorded among the Chichiklia flooded biotopes, due to the significant salinization of the soils of the floodplain.

In order to determine the tolerance ranges of plant communities an ecological-phytocenotic statistical analysis of the floodplain biotopes of the Tiligul-Bug interfluve rivers was carried out. On biotopes of constant flow, the aquatic vegetation of the Tiligul and Chichikliya rivers is in extreme conditions (zone of intolerance), where hydrophytes can only survive, using the body’s energy expenditures only to maintain basal metabolism (to maintain minimal activity). Wetland vegetation formed by species of wide ecological amplitude is more adapted to significant fluctuations in water level, although environmental factors are in the stress range (comfort zone), still plants are able to grow, develop and multiply. Swamp-meadow and partially meadow vegetation as proved to be the most adapted to the existing environmental factors of flooded biotopes, therefore, for them the current ecological and hydrological environmental factors are optimal and contribute to minimal energy consumption of plants and their effective life.

It has been established that, basically, optimal conditions have developed for the growth of swamp-meadow and meadow vegetation. Typical marsh plant communities formed by water and wetland species are located in zones of comfort and pessimum, which is not typical for a typical flooded landscape. Thus, the current environmental conditions of typical flooded vegetation of small and medium-sized steppe streams are not optimal.

The prospects for further investigations are seen in more detailed ecological-hydrological and ecological-botanical studies of the steppe rivers’ marsh vegetation of southern Ukraine to prevent further degradation.