The dynamics of any given plant community are closely related to the population ecology of the principal plant species, but these had hardly been studied in Central Asian plants. The outcomes of long-term studies in the dry steppes of Central Mongolia have shown that the simplification of steppe communities has taken place over recent decades. Annually since 1976, the detailed research of pascual ecosystems in the main natural zones Mongolia are carried out here within the framework of Russian-Mongolian Biological Expedition’s program. Changes of dominant and co-dominant species of pasture plant communities occur corresponding to a dried steppe type. The estimation of present state of natural grasslands was given. The area of different degree of anthropogenic disturbance was discovered. Steppes and dry steppes of Mongolia are characterized by highly dynamic and extreme natural conditions. The results of our survey has showed degradation of vegetable communities for 35-40 years’ period in connection with overgrazing and strengthening of climate aridity in the last decades. The succession of pastoral ecosystems leads to replacement of ecological niches of fodder grasses with uneatable and poisonous species. It results in unsuitability of such pastures for grazing.