2 results
Dynamics of paleoenvironments in the Cis-Ural steppes during the mid- to late Holocene
- Olga Khokhlova, Nina Morgunova, Alexander Khokhlov, Alexandra Golyeva
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- Journal:
- Quaternary Research / Volume 91 / Issue 1 / January 2019
- Published online by Cambridge University Press:
- 11 June 2018, pp. 96-110
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The multi-layered settlement of Turganik in the Tok River valley (steppe region west of the Urals) has been studied using paleopedological and microbiomorphical methods. Early humans lived in the settlement during the Eneolithic epoch (the fifth millennium BC) and in the Early Bronze Age (the fourth millennium BC). The cultural layers attributable to the Atlantic period of the Holocene developed under conditions of a rather dry climate, with the landscapes being dominated by the grass and herb steppe. The settlement area was above the flood water level and was suitable for habitation. The soils in its vicinity were Kastanozems (Endosalic Protosodic). The final stages of the cultural layer formation bear traces of strong (though short-term) floods, with the deposits of the latter partly concealed traces of the preceding long-term arid phase. Maximum aridity was during the final interval of the Atlantic period. The Subboreal and Subatlantic periods were noted for meadow-chernozem soil formation (Luvic Chernozems [Stagnic]) and an increasing proportion of arboreal species in the pollen assemblages. Some phytoliths of aquatic plants were found in the assemblages dominated by those of meadow grasses. The climate was more humid and cool, although short episodes of aridity were possible.
14C Dating to Study the Development of Soils in the Forest-Steppe of the Central Russian Upland as a Result of Bioclimatic Changes and Long-Term Cultivation
- Yury Chendev, Aleksandr Aleksandrovskiy, Olga Khokhlova, Vadim Skripkin
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- Journal:
- Radiocarbon / Volume 60 / Issue 4 / August 2018
- Published online by Cambridge University Press:
- 16 May 2018, pp. 1185-1198
- Print publication:
- August 2018
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Temporal changes in soils of forest landscapes of the forest-steppe zone—Haplic Luvisols and Greyzemic Phaeozems—under the impact of Holocene climate changes (natural factor) and long-term cultivation (anthropogenic factor) were studied on level interfluves of the Central Russian Upland. These soils were developed from covering loesslike loam of varying thickness. To study soil evolution under the impact of climate changes, soil chronosequences of archaeological sites—paleosols buried under ramparts of ancient settlements and background surface soils of adjacent areas—were analyzed. The time of the soil burying was determined via the 14C dating of charcoal from thin twigs sampled in the material of ramparts immediately above the surface of buried soils. According to 14C dates, the paleosols were buried in the interval from 2450±40 to 1150±110 BP. Before the Subatlantic period, these paleosols developed under grassland (steppe), which is proved by their properties typical of steppe soils and by the presence of paleokrotovinas—the features created by the burrowing activity of steppe animals (mole rats)—in the studied profiles. The 14C dates of the total organic carbon of humus in the dark gray filling of a paleokrotovina from a Phaeozem buried at the depth of 140–150 cm under the rampart of 1150±110 BP in age ranged from 6080±150 to 2810±60 BP. The evolution of steppe Chernozems into forest Phaeozems and Luvisols took place in the Late Holocene. The anthropogenic evolution of forest Luvisols and Phaeozems under the impact of long-term (more than 150–230 years) plowing was analyzed in the soil agrochronosequences that included background soils under native forest vegetation and their arable analogs with different durations of cultivation. It was concluded that this evolution is directed towards Chernozemic pedogenesis, i.e., it proceeds in the direction opposite to the natural trend of pedogenesis in the Late Holocene. This process takes place despite the traditional practice of limited application of organic fertilizers in arable farming in the studied region. A decrease in the mean residence time (MRT) of total organic carbon (TOC) in the old-arable soils is considered a consequence of the formation and accumulation of fresh humus material in the profiles of cultivated soils—one of the major processes in the transformation of arable forest soils into Chernozems. The accumulation of carbonates and an increase in their 14C age take place in the arable soils in comparison with their forest analogs. In the agrochronosequence from the Polyana site, the 14C age of carbonates at the depth of 170–180 cm reaches 8000±100, 8270±150, and 9150±100 BP under the forest, 100-year-old plowland, and 150-year-old plowland, respectively. This can be explained by the ascending migration of ancient carbonates from the parent material in suspensions. In the analogous Samarino agrochronosequence, the 14C age of carbonates from the depth of 90–100 cm comprised 6500±90, 7150±100, and 12,360±230 BP, respectively. Thus, the studied forest-steppe soils have a polygenetic nature specified by a complicated history of pedogenesis under the impact of both natural (climate-driven forest invasion into steppe) and anthropogenic (deforestation and land plowing) factors.