Soil conditions and vegetation cover of the «Oruku-Shynaa» cluster of the «Ubsunurskaya Hollow» reserve (southern part of the Republic of Tyva)

The paper presents the results of the study of soils and vegetation cover of the Oruku-Shynaa cluster, a natural feature of the Ubsunur Hollow Biosphere Reserve, which is a possible acquisition of the UNESCO heritage. The Ubsunur Hollow, the northernmost of the inland basins of Northwestern Mongolia, is the destination of Inner Asia, where nature preserves an exceptional «parade of landscapes» of unusual diversity, which predetermines the creation of biosphere reserves in Russia and Mongolia by a cluster approach. Nine clusters have been created on the territory of the Republic of Tuva (Russia). One of them is Oruku-Shynaa. The purpose of creating the Oruku-Shynaa cluster is to study natural complexes and objects, preserve biodiversity, and carry out long-term environmental monitoring of the reference territories of the Ubsunur Hollow. The background soils are brown desert-steppe soils, which have local hydromorphic manifestations of meadow, saline, and solonetsous soils. The study of the temperature of soils in the middle of summer showed that the most mobile dynamics of soil temperature is observed at a depth of 5 cm from the surface. The reaction of meadow-peaty soil is neutral, in solonchak soils it is strongly alkaline, the humus content in solonchak soil is negligible (0,42%), and in meadow-peaty-humus soil it is quite high (9,24%). There is quite a lot of magnesium in saline soils (up to 29 mmol/100 g of soil), and nitrogen (1,10%) in meadow-peat-humus soil. There is a lack of phosphorus in all soils. The cluster is characterized by a high complexity of vegetation cover, expressed in a combination of phytocoenoses of real (glycophytic), saline (halophytic) meadows, steppes, reed beds and woody shrub vegetation. The soil and vegetation cover of the Oruku-Shynaa cluster of the Ubsunur Hollow Nature Reserve generally reflects the regional specifics of the natural situation of floodplain-channel complexes of arid Central Asian territories. The largest areas are open spaces occupied by halophytic vegetation under brown meadow-desert-steppe soils on lake-alluvial deposits. The introduction of the protected regime caused a restructuring in the structure of phytocoenoses, where signs of waterlogging are observed, peat accumulation in the upper horizon of the soil profile, an increase in dead mass (mortmass) in plant communities; an active salinization process is underway in the soil cover.