V. A. Klimanov

Climate and vegetation dynamics in the tundra and forest zone during the late glacial and holocene

Abstract Analysis of palynological successions has enabled reconstruction of climate variations throughout the Late Glacial and Holocene in the tundra and forest zones of northern Eurasia. Statistical analysis allows estimation of mean annual precipitation, and mean annual and July temperatures, based on palynological assemblages. Thus, the dynamic relationships between climate and vegetation changes can be established. Throughout the Late Glacial and Holocene, climate fluctuations were more dramatic in eastern Europe than in Siberia, primarily as a result of the influence of westerly air masses. In contrast, the “autochthonous” climate of Siberia, dominated by local air masses, was less prone to influence from climate changes elsewhere in the Northern Hemisphere, and shows only an attenuated Younger Dryas signal. Mid-Holocene warming characterizes all of northern Eurasia, although the regions of Siberia most influenced by continental climates show less pronounced cooling during the later Holocene. Sharp changes between summer monsoonal and winter anti-cyclonic regimes characterize the Pacific Maritime region.

Quantitative Holocene climatic reconstruction from Arctic Russia

Vegetation changes reflected in fossil pollen spectra are a primary source of information about climate fluctuations in the past. A statistical-information (transfer function) method based on the correlation of recent pollen spectra with modern climate conditions has been used to reconstruct Holocene climatic changes from fossil pollen. Climatic variables used for the reconstructions are the mean annual, January, July temperatures and annual precipitation. Peat sections with pollen and 14C data from the Arctic Russia were used for the reconstructions. The reconstructed climate fluctuations are similar to the climate changes obtained from many sites in the former USSR. A clear signal for Younger Dryas cooling, 11,000-10,000 yr BP and early Preboreal warming is apparent. The early Preboreal (10,000-9000 yr BP) was the warmest time for sites from modern coastal and island areas. The warm interval occurred in the Boreal period, about 8500 yr BP. According to the reconstructions the warmest time for non-coastal areas was the last half of Atlantic period, 6000-4500 yr BP. Other warm intervals were reconstructed about 3500 and 1000 yr BP. Reconstructions show that warming periods are primarily defined as times of increased summer temperatures, and cooling periods as time of decreased winter temperatures. The precipitation followed the temperatures: during the warming periods precipitation increased and during the cooling periods it decreased. Precipitation maximum, about 100 mm higher than present, are reconstructed for the warmest interval, 6000-4500 yr BP at all sites.

Vegetation and climate history of the Yana River lowland, Russia, during the last 6400 yr

New pollen records and radiocarbon dates from two sites in the Yana River lowlands, Arctic Yakutia, Russia provide reconstructions of vegetation and climate history of this region during the last 6400 yr. The #uctuations in pollen and spores re#ect the local hydrological events and regional climate changes. The data show that larch (Larix dahurica) forests with shrub alder (Alnus fruticosa) and dwarf birch (Betula exilis) dominated the area during the last 6400 yr BP. There is no evidence for tree-line #uctuations at the sites during the latter half of the Holocene. Climate reconstructions made by transfer function from one site show that the warmest time was between 6000 and 4500 yr BP. All climate #uctuations reconstructed at this site correspond well with regional climate changes. ( 2000 Elsevier Science Ltd. All rights reserved.

Vegetation and climate changes around the Lama Lake, Taymyr Peninsula during the Late Pleistocene and Holocene reconstructed from pollen records

A continuous lacustrine sequence from the western part of Lama Lake (69°32′N, 90°12′E), complemented by a peat sequence from the lake catchment provides the first detailed environmental reconstruction for the Late Glacial and Holocene on the Taymyr Peninsula. Scarce steppe-like communities with Artemisia, Poaceae, and Cyperaceae dominated during the Late Glacial. Tundra-like communities with Betula nana, Dryas, and Salix grew on more mesic sites. There are distinct climatic signals, which may be correlated with the Bolling and Allerod warming and Middle and Younger Dryas cooling. The Late Glacial/Preboreal transition, at about 10,000 14C yr BP, was characterized by changes from predominantly open herb communities to shrub tundra ones. Larch forest might have been established as early as 9700–9600 14C yr BP, whilst shrub alder came to the area ca 9500–9400 14C yr BP, and spruce did not reach area before ca 9200 14C yr BP. Spruce-larch forests with shrub alder and tree birch dominated the vegetation around the Lama Lake from ca 9000 14C yr BP. Dwarf birch communities were also broadly distributed. The role of spruce in the forest gradually decreased after 4500 14C yr BP. The vegetation cover in the Lama Lake area became similar to the modern larch-spruce forest ca 2500 14C yr BP. A pollen-based biome reconstruction supports a quantitative interpretation of the pollen spectra. Climate reconstructions obtained with information-statistical and plan-functional-type methods show very similar trends in reconstructed July temperature since ca 12,300 14C yr BP, while precipitation anomalies are less coherent, especially during the Late Glacial–Holocene transition.