Environmental dynamics of the Baraba forest-steppe over the last 8000 years and their impact on the types of economic life of the population

This article offers a reconstruction of the vegetation and climate of the south-western Siberian Baraba forest-steppe area during the last ca. 8000 years. The analysis of palynological data from the sediment core of Lake Bolshie Toroki using quantitative methods has made it possible to reconstruct changes of the dominant types of vegetation and mean July air temperatures. Coniferous forests grew in the vicinity of the lake, and mean July air temperatures were similar to present-day ones between 7.9 and 7.0 kyr BP. The warmest and driest climate occurred at 7.0e5.0 kyr BP. At that time, the region had open steppe landscapes; birch groves began to spread. A cooling trend is seen after 5.5 kyr BP, when forest-steppe began to emerge. Steppe communities started to dominate again after 1.5 kyr BP. Mean July air temperatures lower than now are reconstructed for the period of 1.9e1 kyr BP, and then the temperatures became similar to present-day ones. Comparing the archaeological data on the types of economy of the population which inhabited the Baraba forest-steppe with the data on changes in the natural environment revealed a connection between the gradual transition from hunting and fishing to livestock breeding and the development of forest-steppe landscapes with a decrease in the area covered by forests. The development of the forest-steppe as an ecotonic landscape starting around 5 kyr BP might have contributed to the coexistence of several archaeological cultures with different types of economy on the same territory

Uranium and thorium records in the Holocene high-resolution sediments from Borsog Bay in Lake Hovsgol, Mongolia

[研究報告

Эффективность аскорбата лития на модели хронической алкогольной интоксикации

The alcohol leads to deviant behavior in animals, increases aggression and irreversible degenerative changes in the liver and in the central nervous system. Lithium ascorbate in dose of 5 mg/kg, as well as higher doses (10 and 30 mg/kg), activates adaptive mechanisms normalizing behavioral responses in the tests «open field» and «elevated plus-maze». Histological analysis showed that lithium ascorbate minimize ischemic damage of neurocytes to a reversible state. In general, the use of lithium ascorbate contributes to relief of withdrawal symptoms, inhibited the occurrence of seizures and contributed to preservation of the function of the central nervous system in the model of chronic alcohol intoxication.Исследовано действие аскорбата лития на модели хронической алкогольной интоксикации. Воздействие алкоголя приводит к возникновению девиантного поведения у животных, повышает агрессию и вызывает необратимые дегенеративные изменения в печени и ЦНС. Аскорбат лития в дозе 5 мг/кг, как и в более высоких дозах (10 и 30 мг/кг), активирует адаптивные механизмы, нормализуя поведенческие реакции в тестах «открытое поле» и «приподнятый крестообразный лабиринт». Гистологический анализ показал, что использование аскорбата лития минимизировало уровень ишемического повреждения нейроцитов до уровня обратимого состояния. В целом, применение аскорбата лития способствует купированию абстинентного синдрома, блокирует возникновение судорог и способствует сохранности функции ЦНС в модели хронической алкогольной интоксикации

Late Glacial and Holocene changes in vegetation cover and climate in southern Siberia derived from a 15 kyr long pollen record from Lake Kotokel

In this study a radiocarbon-dated pollen record from Lake Kotokel (52°47´ N, 108°07´ E, 458 m a.s.l.) located in southern Siberia east of Lake Baikal was used to derive quantitative characteristics of regional vegetation and climate from about 15 kyr BP (1 kyr=1000 cal. yr) until today. Quantitative reconstruction of the late glacial vegetation and climate dynamics suggests that open steppe and tundra communities predominated in the study area prior to ca. 13.5 kyr BP and again during the Younger Dryas interval, between 12.8 and 11.6 kyr BP. The pollen-based climate reconstruction suggests lower-than-present mean January (~−38°C) and July (~12°C) temperatures and annual precipitation (~270–300 mm) values during these time intervals. Boreal woodland replaced the primarily open landscape around Kotokel three times at about 14.8–14.7 kyr BP, during the Allerød Interstadial between 13.3–12.8 kyr BP and with the onset of the Holocene interglacial between 11.5 and 10.5 kyr BP, presumably in response to a noticeable increase in precipitation, and in July and January temperatures. The maximal spread of the boreal forest (taiga) communities in the region is associated with a warmer and wetter-than-present climate (<i>T<sub>w</sub></i>~17–18°C, <i>T<sub>c</sub></i>~−19°C, <i>P</i><sub>ann</sub>~500–550 mm) that occurred ca. 10.8–7.3 kyr BP. During this time interval woody vegetation covered more than 50% of the area within a 21×21 km window around the lake. The pollen-based best modern analogue reconstruction suggests a decrease in woody cover percentages and in all climatic variables about 7–6.5 kyr BP. Our results demonstrate a gradual decrease in precipitation and mean January temperature towards their present-day values in the region around Lake Kotokel since that time

Holocene climate changes in southern West Siberia based on ostracod analysis

The study presents a summary of the latest data on ostracod microfaunas from Middle-Upper Holocene lacustrine deposits of southern West Siberia collected from lakes Malye Chany, Bol'shaya Lozhka, Beloe, and paleolake Chicha. A total of 28 ostracod species were identified. The identified ostracod assemblages reveal local variations in the lake ecosystems as well as general trends, which can be correlated with both regional and global climate changes. A cooling episode during the second half of the Subboreal is marked by the transition from a warm-water mesohaline assemblage to cold-water candonid ostracods at ca. 3.4 cal ka BP. The widespread occurrence of mesopolythermophilic ostracod species at 1.9-0.6 cal ka BP indicates the end of cooling and lowering of lake-water level. From 0.6 cal ka BP to present, the ostracod assemblages area characterized by the high specific diversity, which is probably an indication of the increased variability of aquatic ecosystems due to fluctuations in salinity and water levels of the lakes. Climate changes identified by ostracod assemblages are consistent with the climatic trend constrained by early palynological studies. (C) 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved

Environmental Changes of the Aral Sea (Central Asia) in the Holocene: Major Trends

From the 20th International Radiocarbon Conference held in Kona, Hawaii, USA, May 31-June 3, 2009.Changes of the Aral Sea level have been observed in 3 sediment boreholes, 2 outcrops, and associated archaeological sites. The obtained results are supported by 25 radiocarbon dates. Major trends of lake-level changes have been reconstructed in some detail for the last 2000 yr, and additional data provide an outline of fluctuations throughout the Holocene. Several distinct changes are shown to precede the modern, human-induced regression of the Aral Sea. These include: 1) the latest maximum in the 16th-20th centuries AD (53 m asl); 2) a Medieval "Kerderi" minimum of the 12th-15th centuries AD (29 m asl); 3) the early Medieval maximum of the 4th-11th centuries AD (52 m asl); and 4) a near BC/AD lowstand, whose level is not well established. Since then, events are only inferred from sparse data. The studied cores contain several sandy layers representing the lowering of the lake level within the Holocene, including the buried shore-bar of ~4500 cal BP (38 m asl), and shallow-water sediments of ~5600 cal BP (44 m asl), 7200 cal BP (28 m asl), and 8000 cal BP (26.5 m asl).The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Geochemistry of Early Diagenesis in Sediments of Russian Arctic Glacial Lakes (Norilo–Pyasinskaya Water System)

The Russian Arctic region is lacking in studies on geochemical changes reflecting early sediment diagenesis in lake environments. The paper presents new data on the compositions of bottom sediments and sediment pore water from two lakes of the Norilo–Pyasinskaya water system in Arctic Siberia. Lakes Pyasino and Melkoye occupy basins left by glaciers that originated from the Putorana Plateau during the Last Glacial Maximum (LGM). Clayey sediments were continuously deposited in the lakes, and the depositional environment has changed only slightly for the last ca. 20 ka. Two sediment cores with lengths of 4.0 and 3.2 m were collected in Lakes Pyasino and Melkoye, respectively, with a Livingstone-type piston corer providing undisturbed, stratigraphically consistent sedimentary sequences. Their analyses revealed a change from oxidized to reduced conditions at a depth of ~10 cm. The concentrations of Ca2+, Mg2+, Na+, and K+, as well as the HCO3−/Ca2+ ratio in pore water, showed a depthward increase indicating the progressive degradation of organic matter. Another trend was the gradual decrease in SO42− alongside increasing HCO3−/SO42− caused by bacterial sulfate reduction, although this was rather weak, judging by the low concentrations of S (II) bound to Fe-sulfides, H2S, etc. Additionally, the microbial digestion of organic matter caused a release of its mobile components, which led to the enrichment of the water in NO3−, PO43−, and DOC. Most of the analyzed elements (Al, B, Ba, Co, Cu, Mo, Ni, Si, Sr, V, and Zn) reach higher concentrations in the pore water than in the lake water above the water-sediment boundary, which is evidence of diagenetic processes. As a result of redox change, immobile Fe (III) and Mn (IV) natural oxides were reduced to mobile Fe (II) and Mn (II) species and migrated from the solid phase to the pore water, and eventually precipitated as authigenic Fe sulfides and Mn carbonates. The results are useful for better understanding the early diagenesis processes in different geographical settings over the huge Eurasian continent