Humid and cold periods in the last 5600 years in Arid Central Asia revealed by palynology of Picea schrenkiana from Issyk-Kul

Abstract

Central Asia, with its high mountains, despite its location between Europe and eastern Asia remains a data poor area. However, mountain glaciers are strongly affected by global change and have a wide-ranging impact. A new pollen record over the last 5600 years shows the extension of a dry Artemisia steppe around Lake Issyk-Kul, with a slightly wetter period from 4.5 to 2.7 ka BP (less Ephedra). Picea schrenkiana forest growing on north-facing slopes of the northern Tien Shan Range, are exposed to Westerlies-related precipitation. The pollen record of Picea is therefore a very good marker of wetter and cold conditions. A comparison to a nearby synchronous pollen record at a higher altitude indicates that the whole forest belt moved down, and that it was not a downwards extension of the lower forest limit only. Four cold and humid phases were evidenced over the last 5.6 ka: 5.5 ka, 4.2 ka and following centuries, 3.2 ka and following centuries (before the end of the Bronze Age) and finally the Little Ice Age, with the latter two being more strongly expressed. These climatic changes, in agreement with other Arid Central Asia investigations, corroborate the driving role of the Westerlies far inland. Human activities were more intense in the Mid and Late Bronze Age (4.5–3.2 ka) and in the last 800 years, confirmed by archaeological and historical information. Issyk-Kul and surrounding rich pastureland were most likely an important step in the ancient Silk Road.

Interpreting Diachronic Size Variation in Prehistoric Central Asian Cereal Grains

“…The studies on past climate in the Tien Shan region are not always helpful when trying to understand climatic differences between Chap II and Chap I sites as contrasting information is provided. Yet, some datasets tend to show dryer climate during the Chap II occupation and more humid during the Chap I (Hill, 2019; Leroy and Giralt, 2020;Tan et al, 2020).…”

Reviewing the Palaeoenvironmental Record to Better Understand Long-Term Human-Environment Interaction in Inner Asia During the Late Holocene

“…Several of the records drawn from high-altitude lakes (Demske et al, 2009;Heinecke et al, 2018;Schroeter et al, 2020) typically have proxies indicating the human presence and low-level impact through time, consistent with their altitudinal position and catchment size. Multi-proxy studies from large lakes located in regions more intensively inhabited by past populations provide strong evidence for long-term processes of environmental modification and impact by humans (Tarasov et al, 2019;Leroy and Giralt, 2021). A number of the studies were more specifically oriented toward understanding local patterns of anthropogenic environmental change, using multiproxy indicators to examine human impacts (Beer and Tinner, 2008;Zhang et al, 2015;Spate et al, 2022).…”

“…Currently, there is no archaeological evidence for agriculture in the study region at this period; however, given the presence of Neolithic agricultural settlements in the adjacent Kopet Dag foothills of southern Turkmenistan (Harris, 2010), future archaeological testing for early agriculture is required. The most significant early impact are seen in pollen, spore, and charcoal proxies around 4,500 BP at Issyk Kol (Leroy and Giralt, 2021) and Bosten (Tarasov et al, 2019) and are closely associated with the first archaeological evidence for cereal cultivation and agropastoralism across the study region (Doumani et al, 2015;Hermes et al, 2019;Motuzaite Matuzeviciute et al, 2020). In the period 4,000-3,000 BP, 10 of the reviewed records indicated evidence for human impacts, primarily palynomorph, charcoal, and sediment proxies associated with agropastoralist land use across foothills and middle-altitude mountain zones.…”

“…This interpretation may be supported by a lake core on the north side of Issyk Kol, in a large basin east of the Kochkor Valley, where the highest abundances of Glomus spores are between ca. 4,500 and 2,700 BP (Leroy and Giralt, 2021). This period in the Issyk Kol record also has the highest abundances of coprophagous spores (Sporormiella, Podospora, and Sordariatypes) and pollen types that may be associated with grazing including Asteraceae, Rumex, Polygonum, and Plantago, while a peak in micro-charcoal influx may be possible evidence of anthropogenic burning.…”

“…Several studies reconstructed a phase of increased or increasing moisture between ca. 5,000 and 4,000 BP including pollen spectra from Lake Karakul, north-eastern Tajikistan (Heinecke et al, 2018), lithological properties, pollen and chironomid records from Lake Kichikol, south-western Kyrgyzstan (Beer et al, 2007), pollen spectra from Lake Issyk Kol, north-eastern Kyrgyzstan (Leroy and Giralt, 2021), and chironomid spectra from Lake Son Kol, central Kyrgyzstan (Laug et al, 2020). However, other records obtained from the same lakes or studies conducted at other sites in the region suggest contradicting moisture trends.…”