Patrick Schevin

LONG-TERM DYNAMICS OF A MEDITERRANEAN ALKALINE VERNAL POOL (RHONE DELTA, SOUTHERN FRANCE)

Mediterranean vernal pools are threatened habitats that support a number of endangered/ rare plant and invertebrate species. Conservation management of these important habitats is limited by a lack of knowledge, especially concerning their past and present ecological dynamics. A multidisciplinary palaeoecological investigation was conducted on one of the last alkaline vernal pools of the Rhone delta (southern France). Results highlighted the value of a multidisciplinary approach based on several complementary methods, and provide direction for subsequent palaeoecological studies in temporary wetlands. Despite some degradation, fossil assemblages provide an accurate reconstruction of the past ecological dynamics of the vernal pool studied. The pool originated c. 1100 years ago from the infilling of an abandoned palaeochannel and its subsequent fragmentation. It may thus be considered as a legacy of past natural fluvial activity, which ended with the complete channelization and confinement of the River Rhone in 1869 AD. With natural processes disrupted, new pools may need to be artificially constructed in order to preserve the biological communities of alkaline vernal pools of the Rhone delta.

15. Estimates of temperature and precipitation variations during the Eemian interglacial: New data from the grande pile record (GP XXI)

New data were obtained from previously unanalysed Grande Pile core samples (GP XXI) corresponding to the penultimate glacial up to the St. Germain 1 interstadial. Parallel sampling for pollen and carbon isotopes was performed. The biostratigraphy is based on pollen grains as proposed by Woillard (1978) for Grande Pile X. The age scale is from Kukla et al. (1997) except for the start of Eemian, which follows the timing defined by Shackleton et al. (2002). The pollen data were first processed to determine their biome scores. The BIOME4 vegetation model was then run in the inverse mode using the determined biome scores and measured δ13C values as constraints to reconstruct the climate parameters. These results are compared with those previously published and show that the Eemian sensu stricto and more generally the penultimate interglacial period was not stable or uniform contrary to previous terrestrial reconstructions but is in agreement with variations observed in the North Atlantic Ocean.