Vegetation change through glacial—interglacial cycles: a long pollen sequence perspective

Abstract

A core recovered from a thick sedimentary sequence in the Ioannina basin, on the western flank of the Pindus M ountain Range, northwest Greece, presents the opportunity to observe multiple changes in vegetational communities at one locality through a series of glacial-interglacial Q uaternary cycles. The Ioannina 249 record adds to the knowledge of vegetation history of areas of increased topographical variability and precipitation of the western Balkans and provides a complete stratigraphical record that can be compared with that of other long terrestrial sequences and with the marine record. Pollen analytical results are presented as percentages and concentrations, the former providing information on the composition and structure of vegetation, while the latter is considered here to be a reliable indication of vegetation density when changes differing by an order of magnitude are documented. The record shows an hierarchical order of variation in the response of vegetation to environmental change. Higher order of magnitude changes are alternations between forest and open vegetation communities, a reflection of major climatic shifts from interglacial to glacial modes. Superimposed on these oscillations is a lower order variability associated with vegetation changes within interglacial and glacial periods. During forest periods a succession is recorded with Quercus and Ulmus/Zelkova expanding early, followed by Carpinus betulus and also Ostrya carpinifolia/Carpinus orientalis , and finally Abies often accompanied by Fagus . Although individual periods may be characterized by dominance of one or more taxa, the underlying pattern of differential expansion is usually distinct and consistent. Nine forested intervals are distinguished and are assigned local names to facilitate longdistance comparisons and correlations. During open vegetation periods a series of changes is also observed from transitional steppe—forest or forest-steppe vegetation, through grassland steppe communities, culminating in a discontinuous desert-steppe vegetation. In addition to the two ends of the spectrum (forest and desert—steppe), attention is drawn to the intermediate phases representing ‘average’ Quaternary conditions. The Ioannina record is correlated with that of other long sequences from Europe and variation in the response of vegetation with site characteristics is considered. A strategy for long-distance correlations relying on the primary structure of vegetation and relative stratigraphical position of individual periods is described. The last interglacial period followed by two interstadials is recorded in much the same fashion in all records. Correlation of earlier periods was also in general agreement although only two continuous records that extend beyond the last interglacial are at present available for comparison. To minimize elements of circularity, similarities in the behaviour of individual taxa during particular periods are not part of the correlation criteria so that if their chronostratigraphical equivalence is independently corroborated their significance can be examined. On this basis, the importance of Carpinus betulus and the almost complete absence of Fagus on a subcontinental scale during the last interglacial are noted. Possible effects of climate, competition and disease are discussed. Cross-correlation with the deepsea oxygen isotope record provides a tentative chronology for the Ioannina record. Based on this, the sequence down to a depth of 162.75 m is considered to represent a record of approximately the past 423 000 years. Aspects of land-sea correlations are discussed in the light of the Ioannina 249 record and the importance of long sequences in the development of European Quaternary stratigraphy is emphasized.

Ostracode-based aminostratigraphy and aminochronology of a tufa system in central Spain

“…correlates well with both OIS 7e and the Zitsa event of the Ioannina Basin (Greece) (Tzedakis, 1994). Aminozone 3 (181 ± 17 ka RP.)…”

“…can be placed at the beginning of the 4th warm and arid period established by Ortiz (2000) and Torres et al (2003a) for the southern part of the Iberian Peninsula, which corresponds to the Holstein Interglacial of the European glacial chronology. It can also be correlated with OIS 11 (Shackleton, 1995), and with the Dodoni Episode (warm) established in the Ioannina Basin (Greece) (Tzedakis, 1994).…”

Mitochondrial phylogeography of the edible dormouse (Glis glis) in the western Palearctic region

“…1). could have been associated with increased aridity during cold periods (Tzedakis 1994), which probably influenced the distribution of suitable habitat (woodlands) for G. glis, leading to fragmentation of populations. However, it also is possible that sampling bias in this study could have artificially depressed measures of genetic diversity in the Balkans.…”

Were Western European Neandertals Able to Make Fire?

“…Similarly, recent data (Veraverbeke et al 2017) and modelling (Romps et al 2014) also suggest that lightning frequency and lightning-caused wildfires are associated with current global warming. Furthermore, we know that the major cold (glacial) and warm (interglacial) oscillations (and the shorter-term variations within these) that occurred in the Pleistocene clearly resulted in changes in temperature, humidity, and plant biomass and moisture: this has been abundantly documented in the paleontological, palynological, and geological record of Western Europe (e.g., de Beaulieu and Reille 1989;Discamps 2014;Discamps et al 2011;Goni et al 2008;Genty 2008;Guiot et al 1993; Laville 1975; Reille and De Beaulieu 1990;Tzedakis 1994;Woillard 1978). Given what we know about how these variables affect lightning-caused fires today, we can expect that during colder periods in the Pleistocene there was a decrease in both lightning frequencies and the type and quantity of vegetation that would favor the ignition and spread of fire.…”