Post-glacial history of Siberian spruce (Picea obovata) in the Lake Baikal area and the significance of this species as a paleo-environmental indicator

The relative abundances of Siberian spruce (Picea obovata) and total arboreal pollen in pollen spectra from the Lake Baikal region and calculation of a steppe-forest vegetation index place constraints on the past climatic conditions related to permafrost, summer temperatures, precipitation and soil moisture availability. Here we review the data on Picea pollen in sub-recent spectra, the present-day distribution of Picea obovata, and sedimentary records from a number of sites to arrive at a coherent picture of evolution of regional vegetation since the late glacial. The expansion of Siberian spruce along with steppe vegetation dates back to the undivided Bolling-Allerod interval, when this species became dominant in arboreal vegetation. Steppe landscapes persisted in a large part of the Lake Baikal watershed prior to 9.2-9 ka when the expansion of arboreal vegetation took place. Following the Younger Dryas (which seems to have had little effect on regional vegetation and peat accumulation), the role of Siberian spruce steadily declined until 8.6-6.8 ka. In the late Holocene, the abundance of P. obovata rarely exceeded the present-day ratio of ca 2% total arboreal pollen. Departures towards higher Picea abundance and higher steppe-forest index at ca 6-5 and 3-2.5 ka in Selenga Delta area appear to reflect periods with decreased temperatures and higher moisture availability in the southern part of the Lake Baikal watershed. (c) 2004 Elsevier Ltd and INQUA. All rights reserved.