Late Quaternary expansion of Norway spruce Picea abies (L.) Karst. in Europe according to pollen data

Lateglacial and Holocene expansion of Norway spruce Picea abies (L.) Karst. in Europe is reconstructed in steps of 1000 radiocarbon years on the basis of pollen data collected from literature and databases. Pollen thresholds for the Lateglacial of 0%, 1 %, 2%, 5%, and 10% and for the Holocene of 2% were used. Spruce-pollen representation and limitations of pollen data are discussed. We assume that the 2% threshold tracks the advance of the main spruce front but might fail to detect small populations or those present in low density. The history of spruce expansion was distinctly different in northern and southern parts of its range: (1) In NE Europe spruce expanded during the Allerod, reaching southwards to N Byelorussia. During the Younger Dryas spruce populations contracted north of ca 60 degrees N, but expanded strongly in the region approximately 53-60 degrees N, 23-32 degrees E where they declined at the beginning of the Holocene. We infer that the Lateglacial expansion in NE Europe concerned mainly P. abies subsp. obovata. (2) Holocene expansion in N Europe concerned mainly P. abies subsp. abies; southward expansion within the northern range is continuing to the recent millennium. (3) In central Europe spruce expanded vigorously during the Allerod, contracted or stagnated during the Younger Dryas, and then strongly re-expanded during the Preboreal, following the simple expectation that climatic warming had a positive impact on its development. (4) Holocene westward and northward expansion of spruce in its southern range (central Europe) was rapid 10-8 ka C-14 BP, very slow 8-6 ka C-14 BP, and rapid 6-5 ka C-14 BP, when the present-day western limits were reached. (5) The 2% spruce-pollen threshold is too high to detect the fact that the northern and southern ranges of spruce have joined in the Holocene. The persistence of low spruce abundance in the transitional area is explained mainly by the strong anthropogenic deforestation ever since spruce grew there. (c) 2006 Published by Elsevier Ltd.