Early Holocene environments in Altai (based on the paleodata from lake sediments)

The article discusses the results of the study of Early Holocene paleorecords from lake sediment cores from Altai lakes and adjacent territories. Among the studied cores of the lake bottom sediments, the Early Holocene sediments contain lakes Maloye Yarovoye, Kuchuk, Kanas, Khoton-Nur, Karakel-Nur, and Khindiktig-Khol. This paper only considers data from the first four lakes. Bottom sediments were sampled using a bottom sampler. The cores were dated by a radiocarbon method. Based on the results of pollen analysis, indices of plant biodiversity and mean annual precipitation were calculated. The main patterns of changes in the environmental conditions of Altai and neighboring territories in the Early Holocene were revealed. It has been found that low values of alpha-diversity indices for the entire studied territory are typical of the Late Dryas (12.9-11.7 ka) and the beginning of the Early Holocene. After 10 ka, phytodiversity also began to increase with the spread offorest and with an increase in the mean annual precipitation. A marked increase in temporal beta diversity expressed in a half change in the taxonomic composition in the steppe Altai for the Late Dryas and Early Holocene (up to 10.2 ka) was observed. In the Mongolian Altai, changes in temporal beta diversity were less pronounced, but also noticeable between 13.3 and 11.6 ka. We have made a conclusion that the Pleistocene-Holocene boundary in the Altai Mountains was characterized by a partial and up to half change in the taxonomic composition of plant communities. The Early Holocene of the study area was shown to be predominantly arid, and even in the Early Holocene, the Altai climate was not influenced by the Asian monsoon. This is evidenced by a marked increase in the mean annual precipitation no earlier than 8 ka. The obtained results make a great contribution to the discussion of the time and limits of the influence of the Asian monsoon on the climate of the Altai Mountains and Central Asia as a whole during different Holocene periods.