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High resolution palaeoecological records for climatic and environmental changes during the last 1350 years from Manzherok Lake, western foothills of the Altai Mountains, Russia
Compilation of spore-pollen, diatom and biochemical analyses of samples from the top 80-cm sediments of Manzherok Lake, located on the western foothills of the Altai Mountains (51°49′15.5″N, 85°48′35.7″E, 400 m a.s.l.), revealed influence of regional climate changes during the past 1350 years on the hydrological budget of the lake and the dynamics of the surrounding vegetation. Based on indicator species of diatom complexes in the lake sediments, the reconstructed lake level and pH can be deciphered as (1) shallow pond with relatively high pH prior to the Medieval Warm Period (MWP), (2) dramatic flooding with freshwater in the MWP, (3) lowering of the lake level during the Little Ice Age (LIA), and (4) contemporary rise of the lake level after the LIA. Increased concentrations of the detrital elements and severe degradation of diatom assemblages in the lake sediments took place during the dramatic flooding stage. The reconstructed lake level based on the diatom assemblages is in good agreement with the palynological data which indicate changes from birch forest-steppe to pine and cedar forests in the beginning of MWP, and then to birch-pine anthropogenically transformed forest-steppe in the LIA. Sharp maxima of non pollen palynomorphs Anabaena and Bryales/Algae at the 43–46 cm depth (∼900 a BP) possibly mark ecological crises in lake's biotope. Cold and dry conditions during the LIA were clearly expressed in pollen diagram of Manzherok Lake by decline of maxima of Siberian pine pollen and increase of Artemisia pollen. This study provides evidence to support a dry episode in the 9th century, wet climatic conditions in the MWP and a dry LIA in the Russian Altai Mountains in contrast to the opposite pattern revealed for arid regions of Central Asia and NW China during the same periods (Chen et al., 2010; Eichler et al., 2011; Chen et al., 2015). Our study indicates that, as a small and shallow lake located in the forest-steppe western foothills of the Altai Mountains, Manzherok Lake is more sensitive to high-resolution (less than centennial scale) climatic and environmental variations, in comparison with the large and deep Teletskoye Lake located in the mountain taiga zone of the northern Altai.