RESULTS OF THE VOLGA RIVER DELTA’S PLANT COVER DYNAMICS RESEARCH, CONDUCTED BY ECOLOGY-BOTANIC PROFILING WITH THE J. BROWN-BLANKE CLASSIFICATION APPROACH USAGE

Barmin Alexander Nikolaevich, Doctor of geographical sciences, professor, head of sub-department of ecology, nature management, land management and life safety, Astrakhan State University (1 Shaumyana square, Astrakhan, Russia), abarmin60@mail.ru
Valov Mikhail Viktorovich, Postgraduate student, Astrakhan State University (1 Shaumyana square, Astrakhan, Russia), m.v.valov@mail.ru

911.2:581.9

10.21685/2307-9150-2016-3-1

Background. Classification is one of the key aspect of land cover research. Many classification systems appeared with development of vegetation science that were worked out by scientists of different geobotanical schools. Many of such systems have definite advantages and disadvantages when studying phytocoenoses in diffe¬rent territories. The most handy and objective was the vegetation classification system on the floristic basis, which achieved the utmost development in the works of a swiss botanist, J. Brown-Blanke. The purpose of the work is to reveal ways and peculiarities of the Volga river delta’s plant cover dynamics under the influence of hydrolgical, climatic and adaphic factors.
Materials and methods. A stationary profile was laid in the eastern part of the Volga river’s estuarine natural system in 1979 including 496 areas with the size of 2×2 m which belong to low, mid and high level grounds. Sample areas were located at the distance of 15 m from each other on the ecotopes, influencing the overflow. Grass stands of each of the interest sites were referred by the types of diagnostic existence to association or subassociation in order to defining plant complex content changes in the stationary profile, which was marked in accordance with the Brown-Blanke classification principals.
Results. The article presents the results of phytocoenosis percentage dynamics, obtained during the plant cover investigations. These investigations were made on the stationary axial section in the Volga River delta from 1979 till 2015 using the J. Brown-Blanke approach. It has been discovered that there was a period of a terri-tory sludging increase in the Volga River delta from the beginning of 1980s till the beginning of 2000s that caused a water-soluble salt content reduction in the ground, also a soil continuum toxic level decrease, a ground water aquifers level increase that lead to a phytocoenosis representation increase, refering to Phragmitetea, Bolboschoenetea maritime and Glycyrrhizetea glabrae and a representation decrease in the grass stand of the vegetation of class Cripsidetea aculeatae of the salt-tolerant type. However at the present stage, a growth of the average annual temperature for a vegetation period together with a contemporary territory sludging decrease lead to the plant cover dynamic processes having a contrary tendency – there is a decrease of the hydrophilous types of vegetation of class Phragmitea and Bolboschoenetea maritime, and appearance in geobotanic descriptions of the association Stachyo-Achilletum septentrionalis (class Molinio-Arrhenatheretea), the presence of which has not been marked in the axial section. Also there are changes in associations’ representation inside a class, particularly, very low overflows in years 2014 and 2015 (84 and 63 cubic km) led to a complete spalling from the grass stand of the association Sparganioerecti-Typhetum angustifoliae (Phragmitetea class), which used to belong to the monodominant before.
Conclusions. The long-term comparative investigations, devoted to revealing the cause-effect relations between meteohydrological conditions and plant cover dyna¬mics, display that since 1979 till 2005 there was a cool-humid Bruckner-type nature cycle in the lower Volga region, which is changing into a warm-dry one at the moment. This aspect should be taken into consideration when planning and correcting the ecosystem exploitation in the Caspian Sea region.

Volga River delta, vegetation cover, vegetation classification, J. Brown-Blanke method.

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