Holocene vegetation and climate history in Baikal Siberia reconstructed from pollen records and its implications for archaeology

Past research has greatly improved our understanding of palaeoenvironmental changes in the Lake Baikal Region, but at the same time has indicated intra-regional variations in this vast study area. Here we present a new AMS-dated late glacial-middle Holocene (ca. 13,500-4000 cal. yr BP) pollen record from Lake Ochaul (54 degrees 14'N, 106 degrees 28'E; altitude 641 m a.s.l.) situated in the less-studied area of Cis-Baikal and compare reconstructed vegetation and climate dynamics with the published environmental history of Trans-Baikal based on the pollen record from Lake Kotokel (52 degrees 47'N, 108 degrees 07'E; altitude 458 m a.s.l.). Although both records show comparable major long-term trends in vegetation, there are considerable differences. Around Ochaul the landscape was relatively open during the Younger Dryas stadial, but forest vegetation started to spread at the late glacial/Holocene transition (ca. 11,650 cal. yr BP), thus ca. 1000 years earlier than around Kotokel. While in both regions taiga forests spread during the early and middle Holocene, the marked increase in Scots pine pollen in the Kotokel record after ca. 6800 cal. yr BP is not seen in that from Ochaul, where birch and coniferous taxa, such as Siberian pine, larch, spruce and fir, dominate, indicating different environmental conditions and driving forces in both study regions. However, the pollen data from Ochaul emphasizes that the Cis-Baikal area also saw a continuous increase in forest cover and in the proportion of conifers over birch trees and shrubs during the early-middle Holocene, which may have contributed to a decrease in the number of large herbivores, the main food resource of the Early Neolithic hunter-gatherer groups. This and rather abrupt reorganization of atmospheric circulation, which affected atmospheric precipitation distribution resulting in thicker and longer-lasting snow cover, may have led to a collapse of Early Neolithic Kitoi populations ca. 6660 cal. yr BP followed by a cultural "hiatus" in the archaeological records during the Middle Neolithic phase (ca. 6660-6060 cal. yr BP). The results stress the importance of sub-regional palaeoenvironmental studies and the need for a representative network of well-dated, high-resolution sediment archives for a better understanding of environmental changes and their potential impacts on the hunter-gatherer populations in the archaeologically-defined micro-regions

Insight into the Last Glacial Maximum climate and environments of the Baikal region

This study presents a multi-proxy record from Lake Kotokel in the Baikal region at decadal-to-multidecadal resolution and provides a reconstruction of terrestrial and aquatic environments in the area during a 2000-year interval of globally harsh climate often referred to as the Last Glacial Maximum (LGM). The studied lake is situated near the eastern shoreline of Lake Baikal, in a climatically sensitive zone that hosts boreal taiga and cold deciduous forests, coldsteppe associationstypical for northern Mongolia, and mountain tundravegetation.The results provide a detailed picture of the period in focus, indicating (i) a driest phase (c. 24.0–23.4 cal. ka BP) with low precipitation, high summer evaporation, and low lake levels, (ii) a transitional interval of unstable conditions (c. 23.4–22.6 cal. ka BP), and (iii) a phase ( c. 22.6–22.0 cal. ka BP) of relatively high precipitation (and moisture availability) and relatively high lake levels. One hotly debated issue in late Quaternary research is regional summer thermal conditions during the LGM. Our chironomid-based reconstruction suggests at least 3.5 °C higher than present summer temperatures between c. 22.6 and 22.0 cal. ka BP, which are well in line with warmer and wetter conditions in the North Atlantic region inferred from Greenland ice-cores. Overall, it appears that environments in central Eurasia during the LGM were affected by much colder than present winter temperatures and higher than present summer temperatures, although the effects of temperature oscillations were strongly influenced by changes in humidity

Biome changes and their inferred climatic drivers in northern and eastern continental Asia at selected times since 40 cal ka bp

Recent global warming is pronounced in high-latitude regions (e.g. northern Asia), and will cause the vegetation to change. Future vegetation trends (e.g. the “arctic greening”) will feed back into atmospheric circulation and the global climate system. Understanding the nature and causes of past vegetation changes is important for predicting the composition and distribution of future vegetation communities. Fossil pollen records from 468 sites in northern and eastern Asia were biomised at selected times between 40 cal ka bp and today. Biomes were also simulated using a climate-driven biome model and results from the two approaches compared in order to help understand the mechanisms behind the observed vegetation changes. The consistent biome results inferred by both approaches reveal that long-term and broad-scale vegetation patterns reflect global to hemispheric-scale climate changes. Forest biomes increase around the beginning of the late deglaciation, become more widespread during the early and middle Holocene, and decrease in the late Holocene in fringe areas of the Asian Summer Monsoon. At the southern and southwestern margins of the taiga, forest increases in the early Holocene and shows notable species succession, which may have been caused by winter warming at ca. 7 cal ka bp. At the northeastern taiga margin (central Yakutia and northeastern Siberia), shrub expansion during the last deglaciation appears to prevent the permafrost from thawing and hinders the northward expansion of evergreen needle-leaved species until ca. 7 cal ka bp. The vegetation climate disequilibrium during the early Holocene in the taiga-tundra transition zone suggests that projected climate warming will not cause a northward expansion of evergreen needle-leaved species

The Early Neolithic–Middle Bronze Age environmental history of the Mamakan archaeological area, Eastern Siberia

This study presents the first radiocarbon-dated palynological record from a peat section (57°49′10.03"N; 114°03′31.37"E, 251 m above sea level) in the Mamakan area located in the lower Vitim River valley, about 350 km northeast of Lake Baikal. While the area is particularly renowned for its numerous multi-layered Upper Palaeolithic (ca. 50,000–14,000/10,000 cal yr BP) archaeological sites with rich cultural assemblages, there is also evidence for human occupation during the Mesolithic–Neolithic–Bronze Age period (ca. 14,000/10,000–3000 cal yr BP). However, the absence of accurately dated palaeoenvironmental records does not allow discussion of prehistoric human–environment interactions in this area. The records of pollen, spores and other non-pollen palynomorphs (NPPs) from the Mamakan site presented in this article document changes in the vegetation and climate of the study area between 6570 and 3630 cal yr BP. From 6570 to 6200 cal yr BP the vegetation around the site was dominated by sparse forests of mainly spruce and larch, indicating that the permafrost layer was located relatively close to the surface. Fir was part of the forest communities in habitats with a milder microclimate and a deeper permafrost layer. Around 6200 cal yr BP Scots pine started to spread across the study area. Until 4670 cal yr BP it dominated the pollen spectra of the Mamakan record, indicating warmer conditions. Climate cooling and higher soil moisture is indicated by the spread of Siberian pine and Siberian dwarf pine at the expense of Scots pine between 4670 and 3840 cal yr BP. From 3840 cal yr BP the Mamakan record suggests a landscape opening associated with the spread of Sphagnum-dominated bog vegetation and an increase in the occurrence of wildfires (3870–3820 cal yr BP), which were either natural in origin or caused by human activities. The spread of Scots pine paralleled by a decline in dark conifers (spruce and fir) and larch in the Lake Baikal Region (LBR) has been linked to a ‘hiatus’ in the Cis-Baikal archaeological records of the Middle Neolithic (6660–6060 cal yr BP). Around the Mamakan site this vegetation change occurred comparatively late, about 600 years later than in the regions around and east (e.g. Lake Baunt area) of Lake Baikal. The Mamakan pollen and NPP records, together with the available archaeological data, suggest that the environmental conditions in the lower Vitim River area may have sustained the hunter-gatherer lifestyle also during the ‘hiatus’ interval

The last glacial maximum and late glacial environmental and climate dynamics in the Baikal region inferred from an oxygen isotope record of lacustrine diatom silica

The last glacial maximum and late glacial environmental and climatic variability in the Baikal region, southern Siberia, Russia has been studied in a sediment sequence from Lake Kotokel, located 2 km east of Lake Baikal, using the oxygen isotope composition of diatom silica (d18Odiatom). The purification of diatom frustules involved the process of trimethylsilylation, which has been shown to be suitable for preparation of diatoms for oxygen isotope analysis. The Lake Kotokel d18Odiatom record presented here spans intervals from about 24.6 to 22.9 ka BP (further referred to as ‘last glacial maximum’) and ~16.7-11.5 ka BP (further referred to as ‘late glacial’) displaying variations in the oxygen isotope composition between +26.7 and +31.2‰. Overall high d18Odiatom values of about +29 to +31‰ during the two investigated intervals characterize a strongly evaporative lake system in a dry environment and suggest a lower than present lake level due to enhanced evaporation. The Lake Kotokel diatom isotope record is roughly in line with the 60° N summer solar insolation, pointing to a linkage to broader-scale climate change, but displays weaker reaction to short-term climatic oscillations, i.e. Bølling-Allerød or Younger Dryas. The climate warming at ~14.3 ka BP is marked by negative spikes in the d18Odiatom record due to isotopically low melt water input from the mountainous hinterland

Pollen data and pollen-based climate reconstruction for the KTK1 pollen record from Lake Kotokel

In this study a radiocarbon-dated pollen record from Lake Kotokel (52°47' N, 108°07' E, 458 m a.s.l.) located in southern Siberia east of Lake Baikal was used to derive quantitative characteristics of regional vegetation and climate from about 15 kyr BP (1 kyr = 1000 cal. yr) until today. Quantitative reconstruction of the late glacial vegetation and climate dynamics suggests that open steppe and tundra communities predominated in the study area prior to ca. 13.5 kyr BP and again during the Younger Dryas interval, between 12.8 and 11.6 kyr BP. The pollen-based climate reconstruction suggests lower-than-present mean January (~ -38 °C) and July (~ 12 °C) temperatures and annual precipitation (~ 270-300 mm) values during these time intervals. Boreal woodland replaced the primarily open landscape around Kotokel three times at about 14.8-14.7 kyr BP, during the Allerød Interstadial between 13.3-12.8 kyr BP and with the onset of the Holocene interglacial between 11.5 and 10.5 kyr BP, presumably in response to a noticeable increase in precipitation, and in July and January temperatures. The maximal spread of the boreal forest (taiga) communities in the region is associated with a warmer and wetter-than-present climate (Tw ~ 17-18 °C, Tc ~ -19 °C, Pann ~ 500-550 mm) that occurred ca. 10.8-7.3 kyr BP. During this time interval woody vegetation covered more than 50 % of the area within a 21x21 km window around the lake. The pollen-based best modern analogue reconstruction suggests a decrease in woody cover percentages and in all climatic variables about 7-6.5 kyr BP. Our results demonstrate a gradual decrease in precipitation and mean January temperature towards their present-day values in the region around Lake Kotokel since that time

Новые данные к реконструкции растительности и климата в Байкало-патомском нагорье (Восточная Сибирь) в максимум последнего оледенения – раннем Голоцене

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Not herbs and forbs alone: pollen‐based evidence for the presence of boreal trees and shrubs in Cis‐Baikal (Eastern Siberia) derived from the Last Glacial Maximum sediment of Lake Ochaul

A new accerator mass spectrometry (AMS)-dated sedimentary record from Lake Ochaul (54 degrees 14 ' N, 106 degrees 28 ' E; 641 m a.s.l.) in Eastern Siberia covers the interval from ca. 27 850 to 20 400 cal a bp at ca. 180-year resolution and contributes to a better understanding of the complex spatial vegetation pattern during the Last Glacial Maximum (LGM). Non-arboreal pollen taxa are abundant in the pollen assemblages (mean value ca. 92.6%), but boreal trees are represented by all major taxa that grow in the lake catchment today, including Betula sect. Albae (0.6-4.8%), Picea (0.6-2.8%), Pinus sibirica (Haploxylon type) (up to 1.5%), Pinus sylvestris (Diploxylon type) (up to 2%), Larix (up to 0.6%) and Abies (up to 0.6%). Betula sect. Nanae/Fruticosae (2-5.2%) and Salix (up to 3.2%) are the most representative boreal shrub taxa. Together with existing modern and fossil pollen data from the wider study region, the current record provides further evidence for the long-debated presence of boreal trees and shrubs in Eastern Siberia throughout the LGM. Our results show that the Upper Lena was a region in which refugia for arboreal taxa existed and that far-distant pollen transport can be ruled out as the source of the detected arboreal pollen

Holocene oxygen isotope record of diatoms from Lake Kotokel (southern Siberia, Russia) and its palaeoclimatic implications

The oxygen isotope composition of diatom silica (d18Odiatom) from marine and lake sediments is helpful for the interpretation of the past climate and environments, especially when complemented by other proxy records. This paper presents a Holocene oxygen isotope record of diatoms from Lake Kotokel, located 2 km east of Lake Baikal in southern Siberia, Russia. The isotope record displays variations in d18Odiatom from +23.7 to +30.3‰ from about 11.5 ka BP until today. Comparing the isotope composition of recent Lake Kotokel water (mean d18O = -12‰) to that of the most recent diatom sample (d18O = +27.5‰), an isotope fractionation in the right order of magnitude was calculated. The Kotokel d18O diatom record is rather controlled by changes in the isotopic composition of the lake water rather than by lake temperature. Lake Kotokel is a dynamic system triggered by differential environmental changes closely linked with various lake-internal hydrological factors. A continuous depletion in d18O of 6.6‰ is observed from Early to Late Holocene, which is in line with other hemispheric environmental changes (i.e. a Mid- to Late Holocene cooling). Enhanced evaporation effects and higher relative supply from a southerly moisture source explain the relatively heavy isotopic composition in a rather cold Early Holocene. In summary, changes in the Holocene d18O diatom record of Lake Kotokel reflect variations in d18O of precipitation linked with both Tair as well as evaporation effects and, to a lesser degree, meltwater pulses from the mountainous hinterland and changing atmospheric moisture sources