The east-west migration of trees during the Eemian Interglacial registered on isopollen maps of Poland

Abstract

The directions of the post-Wartanian (post-Saalian) migration of some thermophilous trees and shrubs into the territory of Poland was reconstructed on the basis of isopollen maps, prepared for the Eemian Interglacial based on the palynological data from 187 Polish pollen profiles. Isopollen maps clearly demonstrated, that all thermophilous trees, which appeared in this area in the early Eemian (Quercus, Ulmus, Fraxinus), migrated from the east or north-east. Also Tilia and Alnus, which arrived in the area of Poland in the middle part of the Eemian Interglacial migrated from the east. Picea, which colonized the territory of Poland twice: first at the very early stage of the interglacial, and then in the younger Eemian, migrated from the east and north-east. Only Corylus, Carpinus betulus and Abies alba migrated from other directions (from the south, from the south-west and from the south-west, respectively). Domination of the western and south-western directions of migration routes clearly differentiates the Eemian Interglacial from the Holocene, during which the majority of trees and shrubs migrated into territory of Poland from the south, south-east, south-west and west, and only a few, such as Ulmus and Picea, also from the east and north-east. We assumed that the most probable reason of this difference was a presence of the Wartanian (Saalian) refugia of many trees, including thermophilous taxa, in the Eastern Europe (west Russia or Black See region). From those regions, together with the decay of the ice sheet, these trees migrated directly into Central Europe along the northern slopes of the Carpathians, or at first migrated to the north via regions which were beyond the maximum range of the Saalian, and from there to the west after the ice sheet melted in this part of Europe.