Carbon isotopic ratios of pollen: interest for palaeovegetations reconstructions.

delta C-13 values of pollen grains belonging to different plant species' (t rees, herbaceous no poaceae, poaceae) were measured. Most of these temperat e species are C3 plants with delta C-13 values between -28.6 parts per thou sand and -21.7 parts per thousand, the C4 plants have more positive values between -15.9 parts per thousand and -10 parts per thousand. These results corroborate the interest of such measurements to differentiate C4 poaceae f rom C3 ones. Inside the same genus or the same species data variability is studied. Chemical treatment (acetolysis) of pollen grains induces a lowerin g of the values. These preliminary results are intended to help calibrate t he pollen grains delta C-13 of modern plants in order to use delta C-13 of fossil pollen grains to reconstruct palaeovegetation variability responses to climatic factors. (C) 2001 Academie des sciences / Editions scientifique s et medicales Elsevier SAS.