Long-term Irrigation Effect on Soil and Vegetation Cover of Floodplain Estuaries in the Southern Urals

The given paper presents the results of long-term (1986-2012) monitoring of the hydrological regime of spring flood, soil, vegetation and productivity of estuaries of the high Sakmar-Tanalyk plain in the steppe zone of the Trans-Urals of the Republic of Bashkortostan. It is found that large water storage reservoirs built in 1986-2012 on the Tanalyk River and its feeders have reduced the amount, frequency and duration of flooding due to high flow and rainfall. It showed lower productivity of natural hayfields from 2.87 to 1.96 t/h as well as the reduction of valuable moisture-loving grasses (wheat grass, slough grass) in the botanical composition of grass from 61 to 32%. It is revealed that the decisive role in replenishing soil moisture reserves of floodplain estuaries takes place during flooding by flood waters. A single spring flooding is found to provide one cut of natural grasses. Long-term flood irrigation (about 30 years) led to 15 cm silt deposit, enriched the upper layers of meadow-Chernozem saline soils (Luvic chernozems sodic) with organic matter and nutrients, and improved the structural and aggregate composition. The salinity quality changed from chloride-sulfate to sulfate-sodic. The salinity level altered from medium to weak.