Palynology and Mediterranean vegetation history

Laura Sadori ,Nathalie Combourieu-Nebout ,Katerina Kouli ,Marta Mariotti Lippi ,Alessio Bertini ,Neil Roberts ,Anna Maria Mercuri

doi:10.7320/flmedit23.141

Abstract

Sadori, L., Bertini, A., Combourieu-Nebout, N., Kouli, K., Mariotti Lippi, M., Roberts, N. & Mercuri, A. M.: Palynology and Mediterranean vegetation history. — Fl. Medit. 23: 141-156. 2013. — ISSN: 1120-4052 printed, 2240-4538 online. The history of Mediterranean vegetation can be outlined using pollen grains contained in lacustrine, marine and other sediments. These sediments have recorded very important vegetation changes during recent geological times. For example, during the last 6 Ma (million years), the effects of different events acting at regional (e.g. the Messinian salinity crisis between 5.96 Ma and 5.33 Ma) and global (expansion of the Arctic ice at ca 2.6 Ma) scales produced a progressive decrease and final disappearance of tropical and subtropical taxa. However, prior to the start of the Quaternary the Mediterranean flora still included a consistent number of tropical and subtropical arboreal taxa accompanying deciduous and partly evergreen trees that have persisted until today. The most important features of the vegetation history of the Quaternary consist in the fact that vegetation adapted to climate changes due to changes in orbital cyclicity, alternating between glacial and interglacial periods. The more widespread vegetation types were steppe and grassland formations during the dry and cold glacial periods whereas either deciduous or evergreen forests were characteristic of interglacial periods. These cold-dry to warmhumid climate cycles became more and more intense towards the present. During the second half of the present interglacial, after the mid-Holocene, joint actions of increasing dryness, climate oscillations and human impact led to the present day Mediterranean plant landscape. It is however not clear how far the causation of this spread of evergreen taxa was climatic or human. One of the most exciting challenges is the prediction of the future course of Mediterranean vegetation. In this perspective a consistent help, not fully explored yet, can be found in aeropalynology, recording the pollen transported in the air. Together with modern surface samples, these data act as modern analogues. Though it probably does not represent the same past vegetational composition, the current pollen rain is the only basic reference on which our comparative approach can rely. Present trends are interpreted and future scenarios can be hypothesized just using a combination of aero- and archaeo-/palaeo-palynological approaches.

Highlights

The Mediterranean basin has always featured, and still has, extremely rich environmental biodiversity (Fig. 1), based both on climate, geology and orography
The history of Mediterranean vegetation can be outlined using pollen grains contained in lacustrine, marine and other sediments
During the second half of the present interglacial, after the mid-Holocene, joint actions of increasing dryness, climate oscillations and human impact led to the present day Mediterranean plant landscape

Summary

Introduction

The Mediterranean basin has always featured, and still has, extremely rich environmental biodiversity (Fig. 1), based both on climate, geology and orography. The natural richness and variety of plants have been enriched and conditioned by the development of human cultures These changes have occurred during the distant past, and in the recent one. 5.9 Ma ago), terrestrial and marine ecosystems were subject to important modifications During this event, warm and dry climate conditions were prevalent in southern areas. A huge amount of data demonstrates that if we consider the vegetation changes that have occurred in the last millennia, the long-term relationships between human cultures, climate changes and landscape ecologies have elicited complex human responses to environmental change since prehistoric times As a matter of fact important changes in Mediterranean vegetation seem to have coincided either with enhanced aridity or with marked increases in social complexity during the Holocene, or with both of them

The origin of the Mediterranean vegetation

Findings

Conclusions