544 ISSN 1064-2293, Eurasian Soil Science, 2020, Vol. 53, No. 5, pp. 544–557. © Pleiades Publishing, Ltd., 2020. Russian Text © The Author(s), 2020, published in Pochvovedenie, 2020, No. 5, pp. 519–534. Reconstruction of Climate and Landscapes of the Medieval Period on the Basis of Palynological Study of Paleosols Buried under Kurgans and Dendrochronological Data from Altai (South of Western Siberia) M. V. Mikharevich a , V. S. Myglan b , and V. E. Prikhodko c, * a Siberian Research Institute of Geology, Geophysics, and Mineral Resources, Novosibirsk, 630091 Russia b Siberian Federal University, Krasnoyarsk, 660041 Russia c Institute of Physicochemical and Biological Problems of Soil Science, Russian Academy of Sciences, Pushchino, Moscow oblast, 142290 Russia *e-mail: valprikhodko@rambler.ru Received June 20, 2019; revised September 3, 2019; accepted December 27, 2019 Abstract—Light loamy ordinary chernozems buried under two kurgans of a large Early Medieval necropolis Srostki-1 constructed in 890 ± 105…975 ± 85 AD (calibration by 1δ) were compared with the chernozem of the background territory in Biysk district of Altai. The analysis of pedological and 20 geochemical indices characterizing weathering, biological activity, and salt leaching demonstrated that the paleosols of the Medi- eval period in the phase before the construction of the kurgans had been formed in a somewhat drier climate compared to the modern conditions, and then the humidization of the paleoclimate began. According to pal- ynological data, the considered period was characterized by a decrease in the area of pine stands, which could be due to colder winters. The areas of birch and riverine willow forests also decreased in comparison with the modern period because of the active cutting by humans of the Srostki ethnos. In the Medieval period, meso- phytic rich forb communities occupied larger areas and predominated over dry-steppe communities. The growth of sedges was active on expanding marshes that appeared after drying of shallow water bodies upon the decrease in the water-protective role of forest vegetation. At the same time, a slight increase in the amount of pollen of xerophytic herbs, including representatives of Chenopodiaceae and Poaceae families and Arte- misia genus took place. This could be related to the increased anthropogenic load, including soil disturbance upon the construction of 61 kurgans of the Srostki culture. Dendrochronological method was applied to reconstruct average summer temperatures over the past two thousand years. It was found that the heat supply of summer seasons in the Srostki period (8th–12th centuries AD) generally corresponded to that at present. However, the years of 850–870 and 930–950 AD were marked by summer cooling, and the years of 876–882 and 982 AD were marked by summer warming with average summer temperatures 1.5°C higher than the ref- erence values of 1961–1990. The climatic variability of the Medieval period in different regions of the south of Western Siberia attests to the metachronous dynamics of the climate specified by the local conditions against the background of general climatic trends typical of Central Asia. Keywords: environmental reconstruction, paleosol, palynology, dendrochronology, kurgans DOI: 10.1134/S1064229320050099 INTRODUCTION Favorable landscape conditions in the transition from plains to the Altai foothills are largely due to a relatively mild climate resulting from the barrier effect. People have settled here since ancient times. Numer- ous Early Paleolithic and later archaeological sites evi- dence this conclusion: the oldest in Russia paleolithic site of Karama [2] and the world-famous monument of Denisova Cave, where people belonging to a sepa- rate branch of the evolution of the genus Homo lived 300 ka BP [55]. In the study region, there are the Srostki Paleolithic site [16] and the large early medie- val necropolis Srostki-1 [9, 31]. Archeologists investigated hundreds of monuments constructed in the second half of the Holocene and identified thousands of kurgans during surveys in the south of Western Siberia and in the Altai Mountains. Only a few of them were studied by methods of geosci- ences. There are scarce data on the climate of the region during the Middle Ages, although it is important for future climate prediction. Recently, some studies have summarized the data on climate of the Middle Ages for several regions [8, 15, 26, 30, 33, 35, 41, 46, 49, 54, 60]. For the Altai region, the environmental reconstruction based on the study of soils buried under kurgans was conducted [3, 5, 10–12, 23, 24, 44]; the approaches described in [7] were used. GENESIS AND GEOGRAPHY OF SOILS