Representatives of nemoral complex are of particular interest among relic species of Siberia. They are preserved as traces of once continuous transpalearctic spread of deciduous forests separating the zone of boreal formations from the steppe zone. In current climatic situation deciduous forests have been replaced by small-leaved forests in the South of West Siberia. Nemoral species here are represented by Tilia cordata Miller and Ulmus laevis Pallas, which are restrictedly distributed in Zaural’ye, as well as relic endemic Tilia sibirica Fischer ex Bayer, characteristic of Gornaya Shoriya, Kuznetsky Alatau and western extremity of Vostochny Sayan. In Vostochnoye Zabaikal’ye deciduous forests are typically replaced with birch forests of Betula davurica Pallas. Among forest-forming arboreal species there have been found local populations of Quercus mongolica Fischer ex Ledeb. in undercurrent of the Argun’ river and a number of Ulmus japonica (Rehd.) Sarg. – Japanese elm isolates gravitating towards forest-steppe regions.
The latter species grows in Selenga Pribaikal’ye, very far away from its Zabaikal’ye habitats in Amur basin. Preservation of this population among mountainous boreal forests is presumably connected with Pitatel’ geothermal refugium at the Selenga river. Elm forests here form small forestlands (from 10 to 25 ha) in the upper flood-lands of the river within a narrow valley between spurs of the Morskoy ridge and Khamar-Daban. These forests are a unique for Baikal basin ecosystem of natural-zonal range carrying relic features in the whole complexity of its component structures (Pleshanov et al., 2008). It should be noted that 8 species of vascular plants and fungi habituating these forests have been listed in “The Red Book of Buryatiya Republic” (2002).
Apparently under favorable climatic conditions species of nemoral dendroflora have successfully overcome Baikal mountainous biogeographical barrier, both in eastern and western directions entraining a suite of accompanying plants and animals. Judging by contemporary findings of Euonymus sacrosancta Koidz. and Daphne mezereum L. valleys of the Angara and Irkut rivers and southern shore of Baikal could have served corridors for such migrations between Predbaikal’ye and Zabaikal’ye. Atlantic period of Halocene is the most probable time of distribution of nemoral ecosystems and, consequently, formation of Selenga elm-forests. Indeed, judging by palinological data, at the end of Pleistocene southern shore of Baikal and Verkhneye Priangar’ye were occupied with forest-tundra and northern taiga preventing preservation of nemoral relics, whereas during climatic optimum of Holocene deciduous formations of oak, linden and elm were to be found both in intermountain troughs of Yuzhnoye Pribaikal’ye, and in the valleys and low plateaus of Priangar’ye (Belova, 1985). Molecular-biological genetic approaches have been proven promising for specification of time periods of formation of nemoral biota refugii in Baikal region.
The research was conducted with support of the grant of Presidium RAS Program ą 23.1.1.
Note. Abstracts are published in author's edition