Stable isotope ratios of carbon and nitrogen in pollen grains in order to characterize plant functional groups and photosynthetic pathway types

Authors

  • Chantal Descolas-Gros,

    1. Institut des Sciences de l’Evolution (UM2-CNRS), Université Montpellier 2, Place Eugène Bataillon, Case Courrier 061, 34095 Montpellier cedex 05, France;
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  • Christian Schölzel

    1. Laboratoire des Sciences du Climat et l’Environnement (LSCE/CNRS) Orme des Merisiers, Bat. 701 91191 Gif-sur-Yvette, France
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Author for correspondence: Chantal Descolas-Gros
Tel:+33 467 14 49 39
Fax:+33 467 04 20 32
Email: descolas@isem.univ-montp2.fr

Summary

  • • Measurements of δ13C, δ15N and C : N ratios on modern pollen grains from temperate plants, including whole grains as well as extracted sporopollenin, were analysed in order to characterize physiological plant types at the pollen level and to determine the variation of these parameters in modern pollen grains of the same climatic area.
  • • Measurements are presented for 95 batches of whole modern pollen from 58 temperate species and on the stable fraction of modern pollen grains, chemically extracted sporopollenin, for two modern species. Fourier transform infrared (FTIR) and cross-polarization and magic-angle spinning (CP/MAS) sporopollenin spectra were conducted in parallel.
  • • C3 and C4 plants can be separated by δ13C measurements based on pollen. Probabilistic assignments to plant functional groups (herbaceous, deciduous woody, evergreen woody) of C3 plants by the means of a discriminant analysis can be made for C : N ratios and for δ13C. The results are related to other studies on sporopollenin in order to use this method in future work on fossil samples.
  • • Stable isotope measurements on pollen allow improved pollen diagrams, including forms that cannot be differentiated at species level, increasing the accuracy and resolution of plant physiological type distribution in quaternary and older fossil sediments.

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