The environment of the Early Iron Age at the southern fringe of the forest zone of the Russian plain

摘要

Landscape response to the Late Holocene climatic cycles was studied on the base of detailed morphological, analytical and micro-biomorphic research of a soil buried under fortification earth wall of the Early Iron Age (around 2000 yr. B.P) and a surface soil. Both soils formed on similar surfaces with the same lithology (mantle loam underlain by calcareous loess), at the same elevation, and in close proximity to each other. The buried soil has a complete profile that was influenced by human activity prior to the burial and subjected to diagenesis after the burial. In addition, both soils (Retisols) show similar morphology and key analytical features indicating close similarity of the landscapes in the study area that existed in the Early Iron Age and those that are present nowadays. Micro-biomorphic assemblages (phytoliths, pollen, microbial genes) support this conclusion. Landscape stability at the southern fringe of the forest zone makes it possible to establish the northern limit of the wide belt, which stretches out from dry steppe to northern forest-steppe, where landscape shifts influenced by the Late Holocene climatic cycles occurred. The features of the diagnostic horizons of the studied Retisols are indicators of stability in the studied time/space range. The study of microbial genes, which was performed in the studied soils for the first time, showed that both content and taxonomic structure of soil microbial communities, are promising paleoclimatic proxies as well as a record of diagenetic changes in buried soils.