Holocene environments and climate in the Mongolian Altai reconstructed from the Hoton-Nur pollen and diatom records: a step towards better understanding climate dynamics in Central Asia

Abstract

a b s t r a c tThis study presents the results of the palynological and diatom analyses of the sediment core recovered in Hoton-Nur Lake (48 37 0 18 00 N, 88 20 0 45 00 E, 2083 m) in 2004. Quantitative reconstruction of the Holocene vegetation and climate dynamics in the semiarid Mongolian Altai suggests that boreal woodland replaced the primarily open landscape of northwestern Mongolia at about 10 kyr BP (1 kyr ¼ 1000 cal yr) in response to a noticeable increase in precipitation from 200-250 mm/yr to 450-550 mm/yr. A decline of the forest vegetation and a return to a predominance of open vegetation types occurred after 5 kyr BP when precipitation sums decreased to 250-300 mm/yr. Prior to 11.5 kyr PB diatom concentrations are relatively low and the lake is dominated by planktonic Cyclotella and small Fragilariaceae, suggesting the existence of a relatively deep and oligotrophic/mesotrophic lake. The great abundance of Staurosirella pinnata from the beginning of the record until 10.7 kyr BP might imply intensified erosion processes in the catchment and this is fully consistent with the presence of scarce and dry vegetation and the generally arid climate during this period. From about 10.7 kyr BP, more planktonic diatom taxa appeared and increased in abundance, indicating that the lake became more productive as diatom concentration increased. This change correlates well with the development of boreal woodland in the catchment. Decrease in precipitation and changes in the vegetation towards steppe are reflected by the rapid increase in Aulacoseira distans from about 5 kyr BP. The Holocene pollen and diatom records do not indicate soil and vegetation cover disturbances by the anthropogenic activities, implying that the main transformations of the regional vegetation occurred as a result of the natural climate change. Our reconstruction is in agreement with the paleomonsoon records from China, demonstrating an abrupt strengthening of the summer monsoon at 12 kyr BP and an associated increase in precipitation and in lake levels between 11 and 8 kyr BP, followed by the stepwise attenuation of the monsoon circulation and climate aridization towards the modern level. The records from the neighboring areas of Kazakhstan and Russia, situated west and north of Hoton-Nur, demonstrate spatially and temporally different Holocene vegetation and climate histories, indicating that the Altai Mountains as a climate boundary are of pivotal importance for the Holocene environmental and, possibly, habitation history of Central Asia.

Asynchronous evolution of the Indian and East Asian Summer Monsoon indicated by Holocene moisture patterns in monsoonal central Asia

“…130°E 120°E 100°E 110°E 90°E 80°E 70°E 20°N 30°N 40°N 50°N 130°E 120°E 100°E 110°E 90°E 80°E 70°E 20°N 30°N 40°N 50°N 130°E 120°E 100°E 110°E 90°E 80°E 70°E 20°N 30°N 40°N 50°N 130°E 120°E 100°E 110°E 90°E 80°E 70°E 20°N 30°N 40°N 50°N 130°E 120°E 100°E 110°E 90°E 80°E 70°E 20°N 30°N 40°N 50°N 130°E 120°E 100°E 110°E 90°E 80°E Whilst maximum moisture conditions are concentrated in southwest China, records from Mongolia, Inner Mongolia and Xinjiang indicate moderately dry conditions consistent with a period of low lake levels observed by Chen et al (2008). However, newly published climatic data from two Mongolian lakes, Hoton Nur (Rudaya et al, 2009) and Lake Hovsgol (Murakami et al, 2009), imply that the early Holocene was characterised by a moisture optimum which is probably indicative of strong spatial differences in the moisture history of Mongolia during the early Holocene.…”

Diatoms (Bacillariophyceae) from the Valley of the Great Lakes in Western Mongolia

“…Importantly, several studies over the last decade have made use of diatoms as paleo-ecological and paleoclimate studies (Tarasov et al, 2000;Peck et al, 2002;Fedotov et al, 2000Fedotov et al, , 2004Rudaya et al 2008;Shinneman et al, 2009a, b,c), highlighting the need for a continued dialog on the taxonomy and ecological distributions of the group. Sampling for the current VOGL survey was designed to develop a diatom calibration model that could be used to interpret historical ecological change in sediment records (Shinneman et al, 2009a).…”

“…Diatom studies by Russian, Mongolian and international scientists have proceeded through the last century (e.g., Skvortzow, 1937;Morales & Edlund, 2003;Metzeltin et al, 2009); however, work has been largely focused on occurrence and distribution with little ecological or applied focus. In recent decades, interest has been building in Mongolia and surrounding regions to use diatoms in paleoclimatological (Tarasov et al, 2000;Peck et al, 2002;Fedotov et al, 2000Fedotov et al, , 2004Rudaya et al, 2008;Shinneman et al, 2009b, c), paleo-ecological (Shinneman et al, 2009a, b;Mackay et al, in press), and ecosystem health assessments (Soninkhishig et al, 1999, Soninkhishig andEdlund, 2001); making an understanding of the distribution and taxonomy of diatoms in Mongolia an important line of study for applied research.…”

OXYGEN ISOTOPE COMPOSITION OF DIATOMS FROM SEDIMENTS OF LAKE KOTOKEL (Buryatia)

“…3) due to mostly Pacific air transport (Kostrova et al, 2013a,b). Spore-pollen data indicate only minor effect of the North Atlantic air transport on the climate of Kazakhstan and southern Siberia at 11-9 kyr BP (Rudaya et al, 2009;Bezrukova et al, 2010). As the monsoon circulation in eastern Eurasia (Yuan et al, 2004) increased during that period (Fig.…”