Main Tendencies in the Dynamics of Floodplain Ecosystems and Landscapes of the Lower Reaches of the Syr Darya River under Modern Changing Conditions

Abstract

The Aral disaster led to the almost complete loss of the Aral Sea. After the construction of the Kokaral dam in 2005, it became possible to rescue the northern part of the Aral Sea (the Little Aral). Due to natural (climatic) and anthropogenic causes, the flow of the Syr Darya River increased in the beginning of the 21st century, its hydrological regime changed dramatically, spring-summer floods decreased, and winter discharges significantly increased. All of these changes strongly affected the dynamics of floodplain ecosystems and landscapes. A comprehensive assessment of current trends in the dynamics of ecosystems and landscapes under changing environmental conditions was attempted in the study. The study was carried out based on field material with data from remote sensing of the Sentinel 2 satellite, as well as climatic and hydrological materials. The office and field data were analyzed according to the developed methodology developed by Zh.V. Kuzmina and S.E. Treshkin for the assessment of transformations in ecosystems and landscapes from natural and hydrotechnical disturbances. The main trends were established as follows: hydromorphic saline formation for the second floodplain level of the river valley; a gradual decrease in the groundwater level, accompanied by a gradual increase in soil salinization with depth and the absence of strong salinization at the top for interstream delta depressions; the withdrawal of the territories from the flood regime without increased soil salinization for the third floodplain level and floodplain terrace; the substitution of a typical perennial grass stand due to its freezing and damping on an annual small weed grass due to winter discharges for the depressions of the first and second levels of the floodplain.