The aim of the study. The aim of the study was to estimate biological productivity of Tyva grasslands. Location and time of the study. The living and dead above- and belowground phytomass, as well as net primary production, were estimated in the montane ecosystems and depressions of the Tyva Republic, Russia. Methodology. Field and laboratory studies of the biological production by grasslands were conducted using botanical, geobotanical and ecological methods. Main results. In the montane ecosystems the aboveground phytomass production was shown to range from 1.3 to 3.6 Mg ha-1 yr-1, whereas the belowground production was evaluated as ranging 10-65 Mg ha-1 yr-1. The belowground production was found to vary widely, being associated with location of mountain ridges, slope geomorphology and grazing, but no association was found with the altitude. In depressions the average green phytomass stock changed from 0.7 to 1.9 Mg ha-1, living belowground phytomass varied 3.4 to 19.3 Mg ha-1. From the meadow steppes to the deserted ones the living above- and belowground stocks decreased 2.7 and 5.7 fold, respectively, whereas the above- and belowground production was estimated to decrease 3 and 4 times, respectively. Several indices to characterize the growth and development, hence the productivity, of herbaceous plants was proposed. The values of the indices calculated for the Tyva grasslands suggested high photosynthetic activity: all studied steppes had the same share of belowground production in the total ecosystem production, i.e. 90%. The turnover rate of the living belowground phytomass was estimated to increase from meadow steppes to the deserted ones, whereas green phytomass increment, as related to its stock, slightly decreased. Conclusions. The living belowground phytomass stock was found to exceed the green phytomass stock by 5-8 times, both in montane ecosystems and depressions. Preservation of living belowground organs during hot dry summers and cold winters, when soil freezes through, is apparently indispensable for grassland survival under any climatic conditions.

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.