Conference:
12th Congress RCMNS, 6 -11 September, Vienna, Austria
Author:
Jean-Pierre Suc, Gonzalo Jiménez-Moreno, Speranta-Maria Popescu, Séverine Fauquette, Stefan Klotz.
Abstract:
An intensive effort was done in the last 30 years for a better knowledge of vegetation and climate in Western-Central Europe and around the Mediterranean Sea, using the most modern approaches in Palynology (reliable botanical identification of pollen grains, high-resolution sampling, expanding counting’s, perfecting appropriate climatic transfer functions, development of pollen databases). A special spreading-up was done during the EEDEN Programme. This results in more to 200 pollen localities for the Neogene period, mostly located in southern Europe, North Africa and Middle East, 15% of which being long pollen sequences covering several millions years (Suc, 1989; Fauquette et al., 1999; Ivanov et al., 2002, Jiménez-Moreno et al., 2005, Suc et Popescu, 2005, Fauquette et al., in press). Accordingly, all the main events of regional (Alp uplifting, Messinian salinity Crisis) or global (climate changes) cause have a response in the pollen records.
On the whole, plant diversity was damaged in losing a lot of tropical-subtropical taxa (especially trees). Their extinctions in this area were mostly N-S forced by repeated climatic coolings but it was not coeval and some meridional persistence areas existed because monsoon influence (Morocco, Turkey) (Suc et al., 2004). On contrary, plant diversity in the Mediterranean region was considerably enriched in herbs as result of climate evolution and environmental splitting up (Pons et al., 1995), the area continuing up today to be a global hotspot in plant diversity (Médail and Quézel, 1999).
Vegetation patterns can be synthetized in: (1) forest cover in West and Central Europe, Northern Mediterranean region northward 42°N in latitude and mountains southward, (2) dry vegetation cover in Mediterranean region southward 42°N in latitude. Such pattern was relatively stable up to the onset of the North Hemisphere glacial-interglacial cycles (2.6 Ma). Then Artemisia steppe vegetation, originating from Anatolia, fasted developed all around the Mediterranean region during glacials.
Climate evolved from tropical-subtropical (wet or dry according to latitude) conditions to temperate conditions trough fluctuations related (1) to 20, 100 and 400 kyrs cycles during the Miocene (Jiménez-Moreno et al., 2003) and the pre-glacial Pliocene (Popescu et al, 2002, in press); (2) to 41 kyrs during the Gelasian (Combourieu-Nebout et Vergnaud Grazzini, 1991). A clear latitudinal gradient, both in temperature and precipitations, already existed over the concerned area at the earliest Miocene. The Mediterranean rhythm (dryness during the warmest season, cool winters) was experienced during the time-window 3.6-2.6 Ma. Then, such seasonality acquired a transitional status. Transfer function provide climatic values (Fauquette et al., 1999, Ivanov et al., 2002, Fauquette et Bertini, 2003; Faiquette et al., in press, Fauquette in Jiménez-Moreno, 2005, Klotz et al., accepted). Reconstructed climatic values confirm and specify the climatic gradients. No major climatic change caused the Messinian salinity crisis.