The vegetation of steppe and forest-steppe belts of the Central Altai
Steppe and forest-steppe belts in Central Altai occupy the bottoms of inter-mountain basins, expanded river valleys and surrounding mountains. The studied 4 steppe sites give sublatitudinal discontinuous range. The Kanskaya basin is rounded, the Ursulskaya one and the Chuya river (lower reaches) valleys are elongated from the east to the west while the steppe site of the Katun river valley - from the south to the north. The Kanskaya basin has a rounded shape while the Ursulskaya basin and the Chuya river valley (lower reaches) are elongated in the latitudinal direction, the steppe site of the Katun river valley - in longitudinal one. The configuration of the surrounding mountains is different: Kanskaya basin is surrounded by gradual mountain ridges with rare outcrops while valley boards of Katun and Chuya rivers are steep and rocky. Steppe belt ((600) 800-1100 m above s. l.) occupies the bottoms of the basins (expanded river valleys) and sun exposed adjoining slopes. Forest-steppe belt (1100-1400 m) occurs on the boards of the basins and includes 2 subbelts: the transitional lower (1100-1200 m) and the main upper (1200-1400 m) ones. It is continuous in the Kanskaya and the Ursulskaya basins and fragmented on the slopes of the Katun and Chuya river valleys. The plant cover structure of each belt is determined by altitudinal types of communities as well as by stands of rocky sites (so called petrophytic steppes). Studied steppes belong to classes Festuco-Brometea (FB) - order Stipetalia sibiricae and Cleistogenetea squarrosae (Cs) - orders Helictotrichetalia schelliani and Stipetalia krylovii. The forest vegetation within the forest-steppe belt goes to Rhytidio-Laricetea (RL) and Brachypodio-Betuletea (BB) and steppe meadows - to Molinio-Arrhenatheretea (MA) - order Carici macrouri-Crepidetalia sibiricae. The phytocoenotic spectra of altitudinal and petrophytic types of communities in steppe and in the upper part of forest-steppe belts are similar in all four sites. The key association in steppe belt is Fragario viridis-Stipetum capillatae (FB). These in the forest-steppe belt are larch herb forests of the ass. Anemonoido caeruleae-Pinetum sylvestris laricetosum (BB), steppe meadows of the ass. Cruciato krylovii-Poetum sibiricae (MA) and the meadow steppes of two vicarious associations - Violo dissectae-Achnatheretum sibiricae (FB) in the Kanskaya basin and Cruciato krylovii-Caricetum pediformis (FB) in three other sites. The petrophytic steppes belong to two associations: Kitagawio baicalensis-Cleistogenetum squarrosae (Cs) on the sun exposed slopes and Galio paniculati-Caraganetum arborescentis (FB) on shadow ones within the steppe belt, and to subass. Carici pediformis-Spiraetum trilobatae schizonepetosum multifidae (FB) that occurs only on sun exposed slopes within the forest-steppe belt. The differences of phytocoenotic spectra of studied sites are determined by the vegetation of the transitional stripe. Forest communities of the ass. Primulo cortusoidis-Laricetum sibiricae (RL) cover the gentle slopes of the Kanskaya and Ursulskaya basins, petrophytic stands of the ass. Carici pediformis-Spiraetum trilobatae schizonepetosum multifidae (FB) occupy rocky sites. Forest communities of the ass. Galio paniculati-Laricetum sibiricae (RL) are common on the steep slopes of the Katun and Chuya river valleys and petrophytic stands belong to the ass. Kitagawio baicalensis-Cleistogenetum squarrosae (Cs). The bottom of the Katun river valley with the very specific mesoclimate is occupied by steppe ass. Artemisio frigidae-Stipetum krylovii (Cs) that in general is not typical for the studied area.