Vegetation of western and southern Mongolia in the late pleistocene and holocene

摘要

Pollen records for 3 freshwater lakes situated in the forest-steppe zone in north-western Mongolia suggest that from 18000-20000 yr B.P. to 9000 yr B.P.treeless vegetation with the dominance of steppe (Artemisia, Chenopodiaceae, Poaceae) and tundra (Cyperaceae, shrub-like forms of Betula and Alnus) taxa covered the area above 2000 m. The driest phase most probably occurred 9000-10000 yr B.P.Vegetation changed rapidly between 9000 and 8000 yr B.P. in response to the climate warming and wetting. In the middle Holocene (4000-8000 yr B.P.) patchy forests dominated by Larix, Picea and Pinus sibirica were characteristic feature of vegetation in the Mongolian Altai at 1700-2500 m a.s.l. All those taxa and Abiew grew together in the Gobi Altai up to 3800 yr B.P. evidenced by the radiocarbon dated plant macroffossils. Pollen and macrofossil records suggest that forest vegetation covered larger area in the Mongolian Altai and in the Gobi Altai during the middle Holocene as compared to today. Southern limit of boreal evergreen coniferous trees was situated much farther to the south from the areas where boreal forests (taiga) in Mongolia grow today. Picea and Abies disappeared from the site in the Gobi Altai between 4000 and 3500 yr B.P. at the same time when the frequency of Picea pollen sharply reduced in the Hoton-Nur record from the Mongolian Altai, suggesting that regional climate became drier than earlier. Vegetation of Western and Southern Mongolia became similar to modern vegetation during the Late Holocene.