Abstracts

Diversity of the Fauna

The section Baika-2 is located in the northern Russian Plain, in the Vychegda River basin near its mouth (61º16’N and 46º44’E). The Vychegda River basin is situated within the zone of middle taiga dark coniferous forest, characterised by temperate continental climate. The mean air temperature at Kotlas (12 km east of the site) in January is -14C, and in July is 17.2 C. The mean annual precipitation at Kotlas is 700 mm.

A sample was collected from the peat layer at the depth of 1.78-1.81 m in the outcrop of the floodplain. Its radiocarbon age is 3,250±65 years BP (Ki-7030). The remains of oribatid mites were separated from the sediment by washing it on 0.1-0.3 mm sieves with running water.

The oribatid mites found in the sample belong to 27 species from 20 genera: Hypochthonius rufulus, Trhypochthonius cladonicola, Malaconothrus punctulatus, Nanhermannia comitalis, Hermannia sp., Tectocepheus velatus, Tectocepheus sp., Autogneta parva, Lauroppia neerlandica, Suctobelba sp., Suctobelbella palustris, S. vera, Oribella pectinata, Cymbaeremaeus cymba, Scapheremaeus palustris, Micreremus brevipes, Oribatula pallida, O. pannonica, Zygoribatula exilis, Z. propinquus, Zygoribatula sp., Liebstadia similis, Scheloribates laevigatus, Sch. latipes, Scheloribates sp. (new), Achipteria sellnicki, Galumna sp. 14 of these species were found in the Holocene deposits in Russia for the first time (underlined). Oribatula pallida has been previously found in Russia only in the Pleistocene deposits in the south of West Siberia.

Analysis of available data on the modern geographical distribution of the fossil Oribatid complex shows that its closest modern analogue can be found in the north-western Russian Plain, in the Sukhona River basin. This region is characterised with more oceanic climate compare to the research site (the mean annual precipitation there is 50 mm greater than at the study site, and mean annual air temperatures is 1ºC higher). The northern limit of the southern taiga coniferous forest, where large peat bogs are widespread, is situated there.

A substantial climatic amelioration in the Subboreal, reconstructed using the Oribatid complex, is corroborated by palynological studies of the same floodplain section (Borisova, in press).

Note. Abstracts are published in author's edition

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