ИСТИНА

Russian Plain in the second half of the Holocene is an area of rhythmic climatic variations. Temporal and spatial variability of climatic changes still remains uncertain. Climatic rhythms entailed the transformation of the whole complex of landscape parameters, including soils. Early Iron Age in the center of the Russian Plain is the time broad penetration of sedentary tribes that introduced the culture of fortified settlements starting from the VII century BC. All studied soils are buried under the fortification earth walls of ancient settlements. Nozha-Var settlement was studied in the deciduous forest area (Chuvash Republic). Three settlements were studied in the central part of the forest-steppe zone (Lipetsk region). The bank of Ksizovo settlement is dated by the 5th century BC, while Mukhino and Degtevoye settlements show two banks each due to multiple uses by successive tribes. In Mukhino there are banks of the 5th century BC and the 5th century AD, in Degtevoye – banks of the 5th and 3rd centuries BC. Altogether soils buried under these banks in similar landscape positions on loess sediments constitute a chronosequence. Borisovka settlement is situated in the southern part of the forest-steppe zone (Belgorod region). Burial time of soils differs from each other for one or two hundred years within the Early Iron Age allowing studying variation of soil properties based on short chronosequences within these ranges, and thus reconstruct climatic trends. The complex landscape dynamics in the second half of the Holocene is revealed based on these studies. Thus, clear unidirectional trend of soil evolution associated with the onset of the forest to the steppe in Sub-Atlantic is recorded in Borisovka settlement. Indicators of such changes are the formation of cutan complex in the the subsoil horizons and the appearance of uncoated sand and silt grains in the lower part of the Mollic horizon. Soil evolution results in the formation of modern polygenetic Luvic Phaeozems with features both of forest and steppe pedogenesis. The study of soil chronosequence in the central part of forest steppe area revealed multidirectional landscape dynamic. The soil buried under the fortification walls of Early Iron Age (5th centuries BC) are similar to modern surface soils – Greyzemic Luvic Phaeozems Loamic. Clay cutans are recorded in the subsoil horizons, and abundance of uncoated sand and silt grains are present in the lower part of the Mollic horizons. The soils buried under the fortification walls of early Middle Ages (5th century AD) are presented by polygenetic Luvic Chernozems. There are no uncoated grains in the Mollic horizon, carbonates are abundant in various forms: impregnation of plasma, soft and hard nodules and carbonate films over clay cutans. Clay cutans proved to be preserved from the previous (forest) stage. Thus, chronosequences of Zadonsk site indicate that the central forest steppe area in the second half of the Holocene experienced landscape dynamics: a change in the conditions of forest to steppe and back to forest steppe. The indicators of such trends are: 1. A complex of clay cutans are already present in the soil buried under the fortification walls of V century BC, indicating that during or before the Early Iron Age soil experienced forest-type pedogenesis. Clay cutans are then inherited by the subsequent stages of evolution till present day; 2. Bleached (uncovered) sand and silt grains in the lower part of the humus horizon. This feature proves to be rather dynamic and can appear, disappear and reappear again; 3. Calcareous profile is dynamic enough feature, subject to reversible changes within the studied space-and-time range. Due to a combination of stable and unstable features the soils of the chronosequence are polygenetic indicating both forest and steppe pedogenesis. In line with morphological and analytical soil features microbiomorphic analyses provide further evidence of environmental dynamic since the Early Iron Age. According to pollen spectrum broad-leaved forests with Tilia dominated in the studied area in 5th century BC. A large number of herbaceous detritus and amorphous organic matter, but a small amount of phytoliths, registered in the spectrum. The content of dicotyledonous grasses reaches 84%, forest cereals - 12%, meadow grass -4%.The composition of the phytoliths complex indicates meadow-forest grass vegetation. The buried soil of the 5th century AD is characterized by the absence of forest cereals and somewhat different ratio of grass species: the content of dicot grains is 91%, meadow grass -9%. As a result, the phytoliths complex can be identified as meadow-grass with participation of deciduous trees. The surface soils develop under the canopy of meadow-forest associations with a high proportion of grasses. The study of Nozha-Var settlement shows that buried and surface soils (Retisols) are quite similar in grain size distribution. Both soils have well developed clay cutans. Carbonates are present deep in the subsoil horizons. Microbiomorphic analyses (pollen, phytolith, microbial genes) also confirm landscape stability since the Early Iron Age. The study of buried soils in the steppe, forest steppe and deciduous forests displayed critical stages of the landscape evolution for the Early Iron Age when short climatic cycles could cause a noticeable change in the environmental parameters, reflected in the properties of buried and surface soils. By ranking soil features in their degree of resistance to the landscape dynamics of the second half of the Holocene a group soil indicators of critical points of evolution was revealed. For instance, humus profile, bleached sand and silt grains, carbonate neoformations can serve as indicators of multi-directional trends of landscape evolution. They can appear and disappear in the studied time-and-space range. Clay cutans are indicators of one-way evolution. In the soils of the central and northern forest-steppe and southern taiga, they could be formed throughout the whole Holocene. However, once appeared, they retain stability even under significant climatic changes and so they are indicators of landscape stability. Thus, in the buried soils of the fifth century AD they are preserved in carbonate horizons, and even covered by carbonaceous films. However, buried soils in the southern forest-steppe area display no clay cutans because they have not been formed here before Sub-Atlantic time. In these landscapes, clay cutans are indicators of the onset of the forest to the steppe. Analyses of soil features as indicators of the landscape dynamics are very promising for soil genetic studies. For example, the surface Greyzemic Phaeozems of the forest-steppe areas are polygenetic and reflect dynamic changes in the border between forest and steppe landscapes. The study of soil chronosequence in the southern part of the forest-steppe area indicates that clay cutans could form rather quickly. In conclusion, the Russian plain in the second half of the Holocene seems to be an arena of complex interactions of different civilizations. Ethnic shifts were largely determined by the climatic rhythms recorded in the buried soils of archaeological sites. In this regard, paleolandscape reconstructions are important for understanding the causes of ethnic shifts and migration waves. Fortification walls of the Early Iron Age and burial mounds of the Bronze Age are not only indicators of landscape dynamics, but also the unique cultural heritage of the East European Plain. Further studies will link the critical stages of evolution with the migration waves of the ancient tribes.