The latitudinal distribution of vegetation cover in Siberia

. The latitudinal changes of vegetation cover on the plains of Siberia are observed. In Western Siberia there are 4 zones (tundra and taiga, and forest-steppe and steppe only here), in Central and North-Eastern Siberia – only 2 zones (tundra and taiga).Tundra zone is represented by 4 subzones in Central Siberia; in Western and North-Eastern Siberia – by 3 subzones (there are no polar subzone). All 5 subzones of the taiga zone are distinguished both in Western Siberia and in the Central Siberia, but in the Central Siberia, forests are found in very high latitudes. The feature of the taiga zone of Western Siberia is high paludification. As a result, the vegetation of mires dominates over the zonal vegetation. Zonal West Siberian types are dark coniferous forests. Light coniferous forests predominate in the taiga zone of Central and North-Eastern Siberia. In t he forest-steppe zone in Western Siberia forests are small-leaved − birch, aspen-birch ( Betula pendula, Populus tremula ). The abundance of mires is the feature of this zone, as well as in the taiga.


Tundra zone
The tundra zone in Western Siberia passes through the Yamal Peninsula, Gydan and the Taz Peninsula. Its southern border reaches the Arctic Circle (66º33'44''N). In Central Siberia, it occupies the Islands of the Arctic Ocean (Northern Land archipelago, etc.) and the Taimyr Peninsula. The southern border of the zone passes here about 72º N, so it is further to the North, than in Western Siberia [4,7]. The tundra zone in North-Eastern Siberia includes the Novosibirsk Islands and the coast of the Arctic Ocean. On the Yano-Indigir lowland, the southern border of the tundra zone runs approximately 70ºN. In the North of the Kolyma lowland it descends slightly to the South up to 68º30'N.
The polar tundra subzone (High Arctic tundra) is absent in Western and North-Eastern Siberia. In Central Siberia it is allocated on the Islands of the Arctic Ocean. Herb-lichenmoss spotted and polygonal gravelly tundra communities with Papaver polare † , Saxifraga spp., Alopecurus alpinus, Phippsia algida, etc. are common. There are no mires.
In the Northern tundra subzone (Arctic tundra), prostrate low shrubs species (Salix and Dryas) play an important role in the vegetation cover. The southern tundra subzone (South hypoarctic tundra) is characterized by the dominance of shrub tundra. In Western Siberia, it reaches 69° N in the North and is bounded by the Arctic Circle in the South. Betula nana and various willows (Salix lapponum, S. phylicifolia, S. dasyclados, S. lanata) are typical for it. In the Central Siberia, this subzone is located much further North and goes from 73° N to the South to 69° N. There are Betula nana and B. exilis; not only Salix glauca, S. lanata, S. pulchra, but also Salix alaxensis, S. boganidensis, Duschekia fruticosa are characteristic. In North-Eastern Siberia in the shrub tundra there is only Betula exilis. In willow communities Salix richardsonii participates along with species specified for Central Siberia. Mires are polygonal herb-shrub-lichen-moss; in Western Siberia there are shrub-moss palsa also.

Taiga zone
In Western Siberia forests have oligodominant structure. Dark coniferous forests predominate, but birch and light coniferous forests are almost equal to them in area. Mires occupy more than 50% of the area. In Central Siberia, the taiga is very different from the taiga of Western Siberia, primarily by the prevalence of light-coniferous larch forests of Larix gmelinii [2,3,5]. In Western and Central Siberia there are 5 subzones, in North-Eastern Siberia − only 2 (there are no subzones of middle, southern taiga and subtaiga). The subzone of the subtaiga in Western Siberia is a narrow strip between 57º and 56ºN. Its peculiarity lies in the dominance of small-leaved native and not secondary forests. Predominate birch (Betula pendula), there are aspen-birch and aspen (Populus tremula) forests. The subzone of the subtaiga in Central Siberia goes from North-West to South-East from 57º N to 52º N along the mountain ranges of Southern Siberia. Pine, larch-pine (Pinus sylvestris, Larix sibirica) forests dominate. Unpatterned fens are the most spread mires type in Western Siberia. Sedge-bryales fens with dwarf birch (Betula exilis) are found in Central Siberia.

Forest-steppe zone
The forest-steppe zone is situated to the South of 56º in Western Siberia. Forests are smallleaved − birch, aspen-birch (Betula pendula, Populus tremula). The second component of the zone is meadow steppes. The abundance of mires is a feature of this zone in Western Siberia, as well as in the taiga. In the extreme South-West of Central Siberia there are small isolated relict forest-steppe islands: Achinsk, Krasnoyarsk, Kansk and Balagan-Irkutsk.

Steppe zone
The steppe zone is fragmentary and expressed only in Western Siberia, fragmentary. South of 54-55ºN part of the territory lies within the northern subzone of the herb-feaver-grasses steppes (Stipa zalesskii, Herba stepposa), small areas in the West and East of the region are located in the middle steppe subzone with more xerophytic feather (Stipa lessingiana) steppes.

Conclusion
So then, in Western Siberia there are 4 zones (tundra, taiga, forest-steppe and steppe, last two are presented only here), in Central and North-Eastern Siberia − 2 (tundra and taiga). Tundra zone is represented by 4 subzones in Central Siberia; in Western and North-Eastern Siberia -by 3 (without polar subzone). All 5 subzones of the taiga zone are distinguished both in Western Siberia and in the Central Siberia, but in the Central Siberia, forests are found in very high latitudes. The feature of the taiga zone of Western Siberia is high paludification. As a result, the vegetation of mires dominates over the zonal vegetation. Dark coniferous forests are zonal West Siberian types. Light coniferous forests predominate in the taiga zone of Central and North-Eastern Siberia. The native birch forests of Betula pubescens and B. pendula are the most characteristic feature of Western Siberia only, whereas in other areas they are appearing as a stage of succession. The abundance of mires is the feature of the forest-steppe zone, as well as in the taiga. Sphagnum raised bogs are extremely characteristic of Western Siberia. In Central Siberia, mari is peculiar feature of the spatial structure of the vegetation cover. Forests of Chosenia arbutifolia and Populus suaveolens in floodplains are specific for North-Eastern Siberia.
Work performed under the target topic of the laboratory of Geography and Cartography Vegetation of Komarov Botanical Institute, AAAAA 19-119030690002-5