The Full-Glacial Forests of Central and Southeastern Europe

Abstract

The presence of trees in central and southern Europe during the last full-glaciation has long been a matter of debate. A low but persistent presence of fossil tree pollen in central and southern European full-glacial paleoecological sequences has been interpreted either as representing long-distance pollen transport from southerly refuges or as representing in situ refugial populations. Here we present macroscopic charcoal results from 31 sequences located throughout Hungary that provide unequivocal evidence for the presence of at least seven different tree types between approximately 32,500 and 16,500 14C yr B.P. This evidence is presented in conjunction with molluscan and pollen analyses to indicate that during the last full-glaciation, trees grew as far north as Hungary, probably in microenvironmentally favorable sites. These areas provided an important cold-stage refugium for the European flora and fauna.

A radiocarbon-dated cave sequence and thePleistocene/Holocene transition in Hungary

“…As a result, it can be assumed that a refugia of temperate forest existed in the analysed region. These data support the earlier palaeoecological and biogeographic analyses [37,56,58,59,79,80,84,88] that more refugia existed in the southern border of the Northern Carpathians where temperate forest habitat and taxon survived the coldest stages of the Pleistocene.…”

“…In addition, numerous charcoal fragments of the so-called thermomesophylic deciduous trees were identified in the sample, pointing to the development of a mixed taiga containing locally such deciduous elements as oak (Quercus) and maple (Acer), for example. These Late Glacial charcoal pieces serve as clear evidence for the local presence of thermomesophylous deciduous arboreal elements in the Late Glacial woodland vegetation of the Carpathian foreland, corroborating the findings of former palynological and malacological studies, which indicated the presence of thermomesophylous woodland refugia in the southern foothills of the Subcarpathian region of the Carpathians [57][58][59][79][80][81][82][83][84][85].…”

“…Therefore, it seems that the Subcarpathian region acted as some sort of dual refugia, offering shelter for the so-called warmthloving species [79] during the glacials and to the socalled cold-resistant elements [79] during the warm periods. These refugial patches must have existed side by side, forming a mosaic that harbored species of different ecological needs in the area [80]. Of course, this issue is more complicated than just simple temperature changes because all ecological factors affect specimens and competition between species and competition within species is also present.…”

Impact of Ice Ages on the genetic structure of trees and shrubs

“…As stated in § 1, such discrepancies between these temperate species are in part related to the location of their glacial refugia that represent the starting points of the postglacial migrational process. Both fossil pollen (figure 3) and macrofossils (Willis et al 2000) indicate, for instance, that birch and alder (figure 3a,b) survived at higher latitudes than oaks (figure 3c), in areas where a supply of moisture was available from the summer melting of ice. Oak trees, on the other hand, were not able to survive in such areas during the last glacial maximum because they are not as cold tolerant as birch or alder.…”

“…Alternatively, other species, such as birches, pines, spruces or willows are cold tolerant and were apparently able to survive the LGM at much higher latitudes. In birches or willows, the fossil pollen record provides very little information on possible LGM refugia and on the fate of the populations after the LGM, and all reliable information might have to come from serendipitous finds of macrofossils (Willis et al 2000;Stewart & Lister 2001;Birks 2003). As we shall see, in the absence of a fossil record, it will be very difficult to make any inference from genetic data alone and it will be difficult to justify the use of a specific demographic model in coalescent-based inferences.…”