| Summary: | According to the reconstructions of plant cover of Siberia, the late glacial was time of domination of cryoarid steppes and tundra-steppes, which existed in the cold and dry climate [1]. Since that time climatic conditions have changed dramatically. However due to current climatic features, the high mountain plateau Ukok (the South-Western part of the South-East Altai, 2 200–3 200 m) is the unique place where the fragments of tundra-steppe landscapes could still exist. The plateau is characterized by temperate sharply continental climate with cool summers and mild winters [8]. To find tundra-steppes, we investigated the vegetation of «oroplacors» and steep southern slopes (possible steppe locations) throughout high-mountain belt (2 200–2 800 m above s.l.); 6 formations were revealed: 1. formation with Kobresia myosuroides dominance; 2. formation with Festuca krylovii and Helictotrichon altaicum dominance; 3. formation with Festuca krylovii and Poa attenuata dominance; 4. petrophytic formation with Carex rupestrisand Festuca tschuensis dominance; 5. petrophytic formation with Artemisia frigidaand Festuca tschuensis dominance; 6. petrophytic formation with Artemisia frigidaandbunch-grass dominance. To determine the phytocoenotic identity of these formations, we analyzed their altitudinal belt spectra. Formation 1 represents mountain tundra (alpine species prevail), formation 6 is steppe (steppe species dominate). The basis of the spectra of formations with Festuca krylovii dominance (formations 2, 3) is formed by alpine and steppe species. According to B. A. Yurtsev’s opinion [10], they must be named the «tundra-steppes». Two petrophytic formations with Festucatschuensis dominance (formations 4, 5) represent cryophytic steppes. On plateau Ukok the tundra-steppes (formation 2, 3) are found out to be altitudinal zonal communities of the low part of high-mountain belt (2 200–2 600 m above s. l.). The background vegetation of the upper part of high-mountain belt (> 2 600 m above s.l.) is Kobresia communities ...
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