Transbaikalian Vegetation

Plant Formations in the Transbaikalian BioProvince

Peter Martin Rhind

Transbaikalian Taiga In the Gremjachaya Valley area these forests can be broadly divided into dark taiga and light taiga. The former is a closed forest dominated by the Siberian endemic fir Abies sibirica (Pinaceae). Other conifers include Picea obovata and the Siberian endemic Pinus sibirica (Pinaceae). These stands can reach heights of over 25 m. Smaller trees are Betula divaricata, Populus tremela and the Siberian endemic Sorbus sibirica (Rosaceae). The same species also form the shrub layer but enriched with Duschekia fruticosa, Ribes nigra, various Salix species and the Siberian endemic Sambucus sibirica (Adoxaceae). The herb layer is relatively rich with various shade tolerant species like Chrysosplenium alternifolium, Saxifraga aestivalis and a variety Equisetum species including E. hyemale, E. pratense, E. sylvaticum and the rare E. scirpoides. Among the flowering plants there are a number of boreal elements including Goodyera repens, Linnaea borealis, Listera cordata and Maianthemum bifolium. Light taiga is a more open forest covering mesic habitats. On slopes between 600-1000 m in the Barguzinskij Range, for example, the main conifer is the Siberian endemic Larix sibirica (Pinaceae), but Betula pendula, Pinus sibirica and P. sylvestris are also common. Characteristic species include the clubmoss Diphasiastrum complanatum and the Siberian endemic Atragene sibirica (Ranunculaceae). On the Lake Baikal islands of Ushkanii, larch forest is common, but here the main species is the endemic hybrid Larix x czekanowskii. It lays midway between the primary ranges of the two parent species Larix gmelinii and L. sibirica, although it has been proposed as an island endemic (L. ushkanensis). The ground layer composition of these forests varies, but in places, particularly in shoreline forest, the dominant species is Vaccinium vitus-idaea. Other common species include Bromopsis pumpelliana, Dendrothema zawadskii, Vicia multicaulis and the Siberian endemic Empetrum sibiricum (Empetraceae). On small islands the grass Brachypodium pinnatum often becomes the most common groundlayer species, while other associated species include Lathyrus humilis, the Siberian endemic Poa sibirica (Poaceae) and the Baikalian endemic Geranium pseudosibirica (Geraniaceae).

Transbaikalian Steppe Steppe is a characteristic vegetation type of the Baikal region where it represents the most northern extension of the central Asian steppe. It is, for example, a conspicuous feature of the Ushkanii Islands. On the other hand, it is extemely varied here and may be dominated by various grasses such as Agropyron cristatum, Koeleria altaica, K. commutata, Helictotrichon desertorum, H. schellianum, Poa botryoides, Stipa capillata or the Siberian endemic Stipa sibirica (Poaceae). Certain forbs are also important such as Alyssum lenense, Artemisia commutata, Dianthus versicolor, Kockia prostrata, Orostachys spinosa, the Siberian endemic Astragalus austrosibiricus (Fabaceae) and the Baikalian endemic Kitagawia baicalensis (Apiaceae). These grasses and forbs can occur in various combinations. However, the most extensive steppe of these islands is co-dominated by Agropyron cristatum and Artemisia commutata. It occurs in the most xeric areas and is a prominent feature of many of the dry, rocky slopes.

Transbaikalian Alpine Tundra Alpine tundra is the characteristic formation of various slopes and summits in the Barguzinkij Range east of Lake Baikal. At elevations ranging from 520-1630 m on slopes and plateaus it can be broadly divided into mat-like stripes in the more exposed areas and dwarf scrub in the wet depressions. On wind swept ridges in the area around the Gremjachaya Valley, for example, the windswept strips largely comprise creeping chamaeophytes, low hemicryptophytes, fructose lichens and mosses with the Siberian endemic or near endemic vascular plant Patrinia sibirica (Valerianaceae) and the lichen Alectoria ochroleuca often representing the most characteristic species. These strips are usually orientated in the direction of the prevailing wind. The height of this vegetation rarely exceeds 5 cm. Other vascular plants may include Artemisia furcata, Bistorta vivipara, Carex ledebouriana, Coeloglossum viride, Gentiana algida, Hierochloe jenisseensis, Kobresia myusoroides, Luzula sibirica, Minuartia arctica, Pedicularis oederi, Poa sibirica, Salix sphenophylla and the endemic Borodinia baicalensis, B. tilingii (Brassicaceae), Calamagrostis korotkyi (Poaceae) and Silene chamarensis (Caryophyllaceae). In slightly wetter areas Dryas punctata becomes more conspicuous. Here the Siberian endemic or near endemic Anemonastrum sibiricum (Ranunculaceae) and Oxytropis alpicola (Fabaceae) occur. The ground layer largely comprises mosses and lichens. In the snow bed areas where snow lies for up to 9 months a year prostrate herbs, grasses, creeping chamaephytes, mosses and lichens predominate with Salix turczaninowii and Sibaldia procumbens often being conspicuous species. However, not surprisingly, these plant formation tend to be species-poor and a shrub layer is largely absent although Betual nana subsp. exilis may be present. Other typical field layer species include Aconogonum ocreatum, Carex podocarpa, Festuca ovina and Luzula cantschadalorum. At ground level, the moss Polytrichum piliferum is usually common but other species likely to be present including lichens like Stereocaulon alpinum. In poorly drained areas, often in shallow depressions on the permafrost, there are Betula nana subsp. exilis shrub formations. Here the main sub-canopy species are hygrophilous mosses such as Sphagnum while vascular plants are represented by just a few species such as Carex bigelowii and Rhododendron aureum. In the better-drained areas Betula nana forms mosaics with alpine grasslands often dominated by Festuca ovina and Anemonastrum sibiricum. Pinus pumila and Betula divaricata stands may also occur. In the undergrowth below the Betula nana lichens such as Cladina stellaris often predominate, while other vascular plants may include Doronicum altaicum, Rhodococcum vitis-idaea and Trollius kytmanovii. The shrubby Betula divaricata stands become more developed in sheltered areas but in other respects these are very similar to Betula nana stands. Finally, there is alpine tundra formations dominated by Bergenia crassifolia and the Siberian endemic or near endemic Juniperus sibirica (Cupressaceae). In the Bol’soj Civyrkuj Valley area this is a rare community of the upper slopes and summits. Species composition of the field and ground layer is limited but may include Campanula rotundifolia, Carex pediformis and Rubus sachalinensis.

Transbaikalian Alpine Grassland and Pinus pumila Scrub Widely distributed in alpine and sub-alpine zones are mosaics of mountain plant formations mainly including grasslands with Festuca ovina and Calamagrostis purpurea and scrub dominated by the dwarf, mountain pine Pinus pumila. There are also patches of dense scrub dominated by the Siberian endemic Juniperus sibirica (Cupressaceae) mixed with Bergenia crassifolia, while in wet depressions hygrophilous species like Bupleurum triradiatum, Carex aterrima and Veratum lobelianum occur. Also common in this zone are patches of scree overgrown with species such as Allium splendens and the Siberian endemics Calamagrostis korotkyi (Poaceae) and Saxifraga bronchialis (Saxifragaceae).

Other species found here include Duschekia fruticosa, Maianthemum bifolium and the endemic or near endemic Astragalus trigonocarpus (Fabaceae), Carex kirilowii (Cyperaceae) and Polygonum baicalense (Polygonaceae).

Transbaikalian Talus (Scree) Formations In the Barguzinskij Range Artemisia lagocephala and the fern Dryopteris fragrans often characterize the vegetation of the siliceous talus slopes and block fields in the alpine zone. A shrub layer is usually absent due to the harsh conditions while the field layer supports only a limited number of vascular plants but may include Empetrum subholarcticum, Ledum palustre, Ribes fragrans, Saxifraga bronchials and the east Siberian endemic Sorbaria pallasii (Rosaceae). In contrast the ground layer is often rich in bryophytes and lichens. At lower levels in the forest belt, conditions on the talus slopes become more favourable allowing a shrub layer to develop in which Rubus sachalinensis becomes an important component, but these are still relatively unstable habitats and most of the species are resistant to disturbance caused by rock movements. In addition to the ones mentioned above species include Calamagrostis langsdorffii, the eastern Siberian endemic Calamagrostis korotkyi (Poaceae) and the two pteridiophytes Selaginella rupestris and Woodsia ilvensis. The ground layer is again rich is bryophytes and lichens.

Transbaikalian Meadow and Tall Forb Communities Various meadow and tall forb communities have been recognized in this BioProvince. In the river valleys of the Barguzinskij Range, for example, at least six categories have been described. In the well-drained but permanently moist floodplains are meadows dominated by the grass Calamagrostis langsdorffii. Other species include Aconitum rubicundum, Alopecurus pratensis, Carex schmidtii, Crepis sibirica, Filipendula palmata, Galium boreale, Lactuca sibirica, Poa sibirica and the endemic Aconitum baicalensis (Ranunculaceae). Such meadows can be found, for example, in the Middle Lena Valley. On the shaded banks of creeks in narrow valleys that are permanently wet, such as the Markuskina Creek, Cardamine macrophylla becomes an important species, while other include Caltha palustris, Chamaenerion angustifolium and Chrysosplenium alternifolium. Along the banks of fast flowing mountain rivers in the lower sub-alpine and forest belts a completely different assemblage occurs. Here in narrow strips the vegetation is dominated by Geranium albiflorum and Pedicularis uncinata. It often occurs in the spaces between boulders often flooded in winter. Other species include Angelica decurrens, Cirsium helenoides, Pleurospermum uralensis, Solidago dahurica, Veratrum lobelianum and the endemic Aconitum baicalensis (Ranunculaceae). Finally in well-drained sub alpine meadows there are tall forb communities dominated by Aquilegia glandulosa and Geranium albiflorum together species such as Acetosa pratensis, Astagalus saralensis, Bupleurum triradiatum, Dracocephalum altaiense, Doronicum altaicum, Saxifraga punctata, Schulzia crinita and Trisetum altaicum.

Transbaikalian Sand Dune Vegetation The dune vegetation around Lake Baikal can be broadly divided into strandline or shoreline vegetation, open sand vegetation and scrub formations of consolidated sand. The shoreline vegetation is a species-poor community dominated by the grass Leymus secalinus and the endemic Craniospermum subvillosum (Boraginaceae). Other species include Aconogonon acreatum, Isatis oblongata and the endemic Festuca rubra subsp. baicalensis (Poaceae). During storms this habitat is often disturbed by waves. On open sand dunes the typical species are Festuca ovina and the endemic Phlojodicarpus baicalensis (Apiaceae) while other less common species are Allium splendens and the Siberian endemic or near endemic Patrinia sibirica (Valerianaceae). Open dunes can be

Copyright © 2010 Peter Martin Rhind found, for example, near to the mouth of the Bol Soj Civyrkuj River, but none of the above- mentioned plants have much influence in stabilizing these dunes. Sand movement appears to be mainly restricted as a result of shelter from adjacent forests of Pinus pumila and P. sibirica. Dune scrub on consolidated sand is mainly dominated by Rosa acicularis and can be found, for example, on the Svatoj Nos Isthmus. Other species found here include Astragalus propinquus, Festuca ovina and Myosotis suaevolens.

Further information required.

References

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