Location and General Description
The ecoregion represents a southernmost latitudinal belt within the subzone of southern taiga in West Siberia which include mixed small-leaf-coniferous, small-leaf and coniferous grass forests. They are the west Siberian part of Hemiboreal forests of North Asia (Hämet-Ahti 1963; Ermakov et al, 1991, 2000). This forest evolved from the ancient Pliocene coniferous-broadleaf forest in situ. In its original composition, it consisted of Pinus spp. with a submixture of other coniferous species such as Picea spp., Abies spp., and Larix spp.; broadleaf species such as Castanea sp., Quercus sp., Tilia spp., Fagus sp., Carpinus sp.,and Ulmus spp.; and small-leaf species such as Populus tremula and Betula spp. After the glacial period, some of the broadleaf species did not survive. Those that survive include: Populus nigra, and in the west of the region Tilia cordata , and in the east of the region Tilia sibirica (Lesa SSSR 1969). The width of this belt is only about 150 km. It does not cover large area, but its biodiversity is highest for western Siberia.
The climate of this ecoregion is moderately continental compared to the taiga zone. Average annual temperature is higher than 0°C. Snow period is 180 days; frost-free period is 100 to 120 days, and spring and autumn are short. Annual precipitation is 350 to 550 mm (Abramovich et al., 1963).
The ecoregion crosses the ancient peneplain that to the east gradually transforms into accumulative plain. The southeastern part of the ecoregion is covered with low mountains (Abramovich et al., 1963). The ecoregion is crossed by the Irtysh and Ob’ Rivers, and their numerous tributaries flow predominantly in south-north direction.
The forested areas of the ecoregion were recently occupied by mixed forests (Abies sibirica, Picea obovata, Pinus sibirica, P. sylvestris and Tilia cordata or Tilia sibirica). The latter species constituted a significant part of the subcanopy, its share in the canopy layer growing from north to south (Volkova 1965; Iljina et al. 1975; Lapshina 1985; Smolonogov et al. 1970). For the grass layer, characteristic nemoral floristic elements include: Aegopodium podagraria, Pulmonaria dacica and Actaea erythrocarpa. As a result of recent intensive exploitation and frequent fires, these communities were almost everywhere replaced by forests with dominated by Betula pendula and Populus tremula or by almost pure Pinus silvestris forests with Tilia cordata in the subcanopy and, as submixture, in the canopy. The latter forest type has a rich grass layer with many nemoral species. Dominant species in different associations are: Calamagrostis arundinacea, Carex macroura, Aegopodium podagraria, Vaccinium vitis-idaea and V.myrtillus. Other common species include: Rubus saxatilis, Maianthemum bifolium, Lathyrus vernus, Galium septentrionale, Equisetum sylvaticum and Angelica sylvestris. Moss cover is not well-developed; the most common mosses are Pleurozium schreberi and Dicranum polysetum
(Lapshina 1985). Primary birch forests occur in the northern part of the ecoregion. Their tree canopy consists of Betula pendula accompanied by Betula alba, Populus tremula and, rarely, Tilia species. Shrub layer include Rosa majalis, Crataegus sanguinea, Sorbus sibirica, Salix caprea, Viburnum opulus, Spiraea media and some others. Dominants of grass cover are as follows Calamagrostis arundinacea, C. epigeios, C. obtusata, Rubus saxatilis, Cnidium dubium, Geranium pseudosibiricum, Vicia cracca, Gentiana pneumonanthe, Delphinium elatum, Trientalis europaea, including nemoral relicts Dryopteris carthusiana, Phegopteris connectilis, Pulmonaria dacica and Aegopodium podagraria. As a whole, the flora of the primary birch forests include about 400 plant species (Lavrenko 1985). Swamps occupy about 20 percent of the ecoregion. Most of them are eutrophic and located at the watersheds. The main dominant in the canopy is Betula alba , although a significant part of these swamps have no trees. In the grass layer, dominants include: Calamagrostis langsdorffii and Carex lasiocarpa. Hypnaceae (Aulacomnium palustre and others) as well as Sphagnum warnstorfii dominate in the moss layer ( Romanova 1985).
High biodiversity is a characteristic feature of this ecoregion. Flora is represented here by south taiga species, nemoral species including some relict species, forested steppe species and even some steppe species. The incomplete list of vascular plants consists of about 1,000 species.
The fauna is also represented by a mixture of taiga and forested steppe species, and by European and eastern Siberian species. This subzone is a corridor along which species move both east to west and west to east, as well as from south to north and north to south. Maybe this explains why there are no endemics in the ecoregion and its flora and fauna are still in the process of being catalogued.
The entire ecoregion has been badly disrupted by human activities. Almost all the original vegetation has been replaced by successional communities. This has led to the rapid decline of Tilia cordata and T. sibirica in forest canopies (Hlopov 1965). Other endangered species include: Cypripedium macranthon, Calypso bulbosa, Epipogium phyllum, Orchis militaris, Trapa natans, Paeonia anomala, Nymphaea candida and other plants ( Redkie I is chezayushchie.., 1980).
For the Irtysh River watershed portion of this ecoregion, there are 283 known terrestrial vertebrate species: 44 mammals, 231 birds and 8 amphibians and reptiles (Vershinina et al. 1975).
Examples of endangered animals include Coregonus tugun, Grus leucogeranus, Strix aluco, and Castor fiber pohlei.
Some original dark coniferous-linden and linden forests with a complex of relict nemoral flora are still preserved in the ecoregion. Nevertheless, due to absence of zapovedniks and national parks in the ecoregion the future of these communities is problematic. Today there are two forest massifs that are protected with the status of nature monuments (Kemerovo oblast’ and Kurgan oblast’), but this is not sufficient. An entire network of protected areas must be established. Of high priority are all preserved massifs of original dark-coniferous-broadleaf, broadleaf forests of the Tavdinsko-Kovdinskaja Plain, and forests between the Tobol and Ishym Rivers (Zelenaja kniga... 1996).
Types and Severity of Threats
Main threats include: clearcuts, frequent fires, poaching and pasturing in forests, which leads to fragmentation or complete destruction of forest ecosystems, and a decrease of flora and fauna diversity.
Justification of Ecoregion Delineation
The West Siberian broadleaf and mixed forest ecoregion is the slim transitional zone between the Siberian taiga and the Kazakh forest steppe. It stretches from the Ural Mountains eastward to the Yenisei River. Ecoregion boundaries correspond to the northern subzone of monodominant forests in the Ural and Western Siberian province of Kurnaev’s forest map the USSR (1990).
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Prepared by: Sergei Ponamarenko
Reviewed by: Olga Zyranova