Description: The northeastern part of Eurasia represents one of Earth‟s most extreme periglacial climate regions, characterized by the strongest seasonal temperature amplitudes on the northern hemisphere. The region is occupied by deep-reaching permafrost and covered by widespread taiga and tundra vegetation (Müller et al., 2010). Paleoenvironmental studies have been conducted close to the northern polar cycle in the Verkhoyansk Mountain Range and its western foreland to infer periglacial landscape dynamics in response to late Quaternary climate change. The distribution of preserved terminal moraines reveal several mountain glacier advances in the past (Stauch and Lehmkuhl, 2010). According to luminescence dating, the widest geologically documented glacial advence took place during the Saalian stage around 135 ka. Less extended glaciations to the foreland appeared during the early Weichselian at 100-120 ka and at 85-90 ka, while the youngest glaciation (〉50 ka) was confined to the mountain area. No regional glacial advance is evident for the late Weichselian and the last glacial maximum, a time which was characterized by aeolian loess formation (Stauch et al., 2007, Popp et al., 2007). Sediment cores from the 25 m deep Lake Billyakh (340 m a.s.l.), a former proglacial basin, document environmental changes of the last 50 kyr (Diekmann et al., 2007). Pollen records indicate a dry climate for the late Weichselian, indicated by a change from tundra towards cold steppe vegetation after 32 ka until 13.5 ka BP (Müller et al., 2009, 2010). For the same time, sedimentological and diatom data indicate a lake level drop. Modelling experiments with a general circulation model suggest that the consecutive decline in the extent of mountain glaciers and increase in dryness through the Weichselian was dictated by the growing shielding effect of the western Eurasian ice sheets that prevented the supply of moist Atlantic air masses to eastern Siberia (Krinner et al., 2011). In addition, enhanced deposition of dust reduced the albedo and promoted ice and snow melting during summer (Krinner et al., 2011). Environmental changes towards interglacial conditions of the Holocene are documented in the Lake Billyakh deposits (Müller et al., 2009) as well as in a peat section at Dyanushka River (Werner et al., 2009). Both records show that climate amelioration started after 13.5 ka BP with the quick return of larch trees that also persisted during the Younger Dryas cold spell, suggesting that the Verkhoyansk Mountain area possibly represented a plant refugium during the climate extremes of the last ice age (Tarasov et al., 2009). Reforestation continued since 11.4 ka BP with the spread of boreal cold deciduous and taiga forests and reached a maximum extent after 7 ka BP. Limnological conditions of Lake Billyakh changed to a higher lake-level and increased biological productivity consistent with climate warming and increased humidity. Mean July air temperatures reconstructed by fossil aquatic chironomids, using a regional inference model (Nazarova et al., 2011), indicate warmest summer temperatures between roughly 9.0 and 6.6 ka BP. The stable-isotope composition of ice wedges in permafrost soils point to warmer winters during the early Holocene compared to the late Holocene (Popp et al, 2006). The recognition of a regional early Holocene climate optimum is consistent with long-term Holocene climate development in wide parts of northern Eurasia. References Diekmann, B., Andreev, A.A., Müller, G., Lüpfert, H., Pestryakova, L., Subetto, D., 2007. Expedition 'Verkhoyansk 2005' - Limnogeological studies at Lake Billyakh, Verkhoyansk Mountains, Yakutia. In: Schirrmeister, L. (ed.): Expeditions in Sibiria in 2005, Reports on Polar and Marine Research, 550: 247-258. Krinner, G., Diekmann, B., Colleoni, F., Stauch, G., 2011. Global, regional and local scale factors determining glaciation. Quaternary Science Reviews, 30: 821-831. Müller, S., Tarasov, P. E., Andreev, A., Diekmann, B., 2009. Late Glacial to Holocene environments in the present-day coldest region of the Northern Hemisphere inferred from a pollen record of Lake Billyakh, Verkhoyansk Mts ., NE Siberia. Climate of the Past 5: 73-84. Müller, S., Tarasov, P.E., Andreev, A.A., Tuetken, T., Gartz, S., Diekmann, B., 2010. Late Quaternary vegetation and environments in the Verkhoyansk Mountains region (NE Asia) reconstructed from a 50-kyr fossil pollen record from Lake Billyakh. Quaternary Science Reviews, 29: 2071-2086. Nazarova, L., Herzschuh, U., Wetterich, S., Kumke, T., Pestryakova, L., 2011. Chironomid-based inference models for estimating mean July air temperature and water depth from lakes in Yakutia, northeastern Russia. Journal of Paleolimnology, 45(1): 57-71. Popp, S., Belolyubsky, I., Lehmkuhl, F., Prokopiev, A., Siegert, C., Spektor, V., Stauch, G., Diekmann, B. (2007): Sediment provenance of late Quaternary morainic, fluvial and loess-like deposits in the southwestern Verkhoyansk Mountains (eastern Siberia) and implications for regional palaeoenvironmental reconstructions. Geological Journal, 42: 477-497. Popp, S., Diekmann, B., Meyer, H., Siegert, C., Syromyatnikov, I., Hubberten, H. W., 2006. Palaeoclimate signals as inferred from stable-isotope composition of ground ice in the Verkhoyansk foreland, Central Yakutia. Permafrost and Periglacial Processes, 17: 119-132. Stauch, G., Lehmkuhl, F., 2010. Quaternary glaciations in the Verkhoyansk Mountains, Northeast Siberia. Quaternary Research, 74: 145-155. Stauch, G., Lehmkuhl, F., Frechen, M., 2007. Luminescence chronology from the Verkhoyansk Mountains (North-Eastern Siberia). Quaternary Geochronology, 2: 255-259. Tarasov, P., Müller, S., Andreev, A., Werner, K., Diekmann, B., 2009. Younger Dryas Larix in eastern Siberia: A migrant or survivor? PAGES News, 17(3): 122-123. Werner, K., Tarasov, P.E., Andreev, A.A., Müller, S., Kienast, F., Zech, M., Zech, W., Diekmann, B., 2009. A 12.5-kyr history of vegetation dynamics and mire development with evidence of Younger Dryas larch presence in the Verkhoyansk Mountains, East Siberia, Russia. Boreas, 39(1): 56-68.

Description: A 415 cm thick permafrost peat section from the Verkhoyansk Mountains was radiocarbon-dated and studied using palaeobotanical and sedimentological approaches. Accumulation of organic-rich sediment commenced in a former oxbow lake, detached from a Dyanushka River meander during the Younger Dryas stadial, at ∼12.5 kyr BP. Pollen data indicate that larch trees, shrub alder and dwarf birch were abundant in the vegetation at that time. Local presence of larch during the Younger Dryas is documented by well-preserved and radiocarbon-dated needles and cones. The early Holocene pollen assemblages reveal high percentages of Artemisia pollen, suggesting the presence of steppe-like communities around the site, possibly in response to a relatively warm and dry climate ∼11.4–11.2 kyr BP. Both pollen and plant macrofossil data demonstrate that larch woods were common in the river valley. Remains of charcoal and pollen of Epilobium indicate fire events and mark a hiatus ∼11.0–8.7 kyr BP. Changes in peat properties, C31/C27 alkane ratios and radiocarbon dates suggest that two other hiatuses occurred ∼8.2–6.9 and ∼6.7–0.6 kyr BP. Prior to 0.6 kyr BP, a major fire destroyed the mire surface. The upper 60 cm of the studied section is composed of aeolian sands modified in the uppermost part by the modern soil formation. For the first time, local growth of larch during the Younger Dryas has been verified in the western foreland of the Verkhoyansk Mountains (∼170 km south of the Arctic Circle), thus increasing our understanding of the quick reforestation of northern Eurasia by the early Holocene.

Description: 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.

Description: The spatial and temporal variability of a low-centred polygon on the eastern floodplain area of the lower Anabar River (72.070° N, 113.921° E; northern Yakutia, Siberia) has been investigated using a multi-method approach. The present-day vegetation in each square metre was analysed, revealing a community of Larix, shrubby Betula, and Salix on the polygon rim, a dominance of Carex and Andromeda polifolia in the rim-to-pond transition zone, and a predominantly monospecific Scorpidium scorpioides coverage within the pond. The total organic carbon (TOC) content, TOC / TN (total nitrogen) ratio, grain size, vascular plant macrofossils, moss remains, diatoms, and pollen were analysed for two vertical sections and a sediment core from a transect across the polygon. Radiocarbon dating indicates that the formation of the polygon started at least 1500 yr ago; the general positions of the pond and rim have not changed since that time. Two types of pond vegetation were identified, indicating two contrasting development stages of the polygon. The first was a well-established moss association, dominated by submerged or floating Scorpidium scorpioides and/or Drepanocladus spp. and overgrown by epiphytic diatoms such as Tabellaria flocculosa and Eunotia taxa. This stage coincides temporally with a period in which the polygon was only drained by lateral subsurface water flow, as indicated by mixed grain sizes. A different moss association occurred during times of repeated river flooding (indicated by homogeneous medium-grained sand that probably accumulated during the annual spring snowmelt), characterized by an abundance of Meesia triquetra and a dominance of benthic diatoms (e.g. Navicula vulpina), indicative of a relatively high pH and a high tolerance of disturbance. A comparison of the local polygon vegetation (inferred from moss and macrofossil spectra) with the regional vegetation (inferred from pollen spectra) indicated that the moss association with Scorpidium scorpioides became established during relatively favourable climatic conditions, while the association dominated by Meesia triquetra occurred during periods of harsh climatic conditions. Our study revealed a strong riverine influence (in addition to climatic influences) on polygon development and the type of peat accumulated.

Description: The current study presents quantitative reconstructions of tree cover, annual precipitation and mean July temperature derived from the pollen record from Lake Billyakh (65°17'N, 126°47'E, 340 m above sea level) spanning the last ca. 50 ka (ca. 50,000 cal yrs). The reconstruction of tree cover suggests presence of woody plants through the entire analyzed time interval, although trees played only a minor role in the vegetation around Lake Billyakh prior to 14 ka BP (〈5%). This result corroborates low percentages of tree pollen and low scores of the cold deciduous forest biome in the PG1755 record from Lake Billyakh. The reconstructed values of the mean temperature of the warmest month 8-10 °C do not support larch forest or woodland around Lake Billyakh during the coldest phase of the last glacial between 32 and 15 ka BP. However, modern cases from northern Siberia, ca. 750 km north of Lake Billyakh, demonstrate that individual larch plants can grow within shrub and grass tundra landscape in very low mean July temperatures of about 8 °C. This makes plausible the hypothesis that the western and southern foreland of the Verkhoyansk Mountains could provide enough moist and warm microhabitats and allow individual larch specimens to survive climatic extremes of the last glacial. Reconstructed mean values of annual precipitation are about 270 mm during the last glacial interval. This value is almost 100 mm higher than modern averages reported for the extreme-continental north-eastern Siberia east of Lake Billyakh, where larch-dominated cold deciduous forest grows at present. This suggests that last glacial environments around Lake Billyakh were never too dry for larch to grow and that the insufficient summer warmth was the main factor, which limited tree growth during the last glacial interval. The nalkane analysis of the Siberian plants presented in this study demonstrates rather complex alkane distribution patterns, which challenge the interpretation of the fossil records. In particular, extremely low n-alkane concentrations in the leaves of local coniferous trees and shrubs suggest that their contribution to the litter and therefore to the fossil lake sediments might be not high enough for tracing the Quaternary history of the needleleaved taxa using the n-alkane biomarker method.