Stomatal density and index of a fossil Platanus



Stomatal density and index data of Platanus neptuni leaf fossils and their evaluation as a CO2 proxy for the Oligocene

by Roth-Nebelsick A., Oehm C., Grein M., Utescher T., Kunzmann L., Friedrich J. P., Konrad W. (2014)

Anita Roth-Nebelsick, a  Christoph Oehm, a  Michaela Grein, b  Torsten Utescher, cd  Lutz Kunzmann, e  Jan-Peter Friedrich, a  Wilfried Konrad, f

State Museum of Natural History Stuttgart, Rosenstein 1, D-70191 Stuttgart, Germany
Übersee-Museum Bremen, Bahnhofsplatz 13, D-28195 Bremen, Germany
Steinmann Institute, Bonn University, Nuβallee 8, D-53115 Bonn, Germany
Senckenberg Research Institute, D-60325 Frankfurt, Germany
Senckenberg Natural History Collections Dresden, Königsbrücker Landstraβe 159, D-01109 Dresden, Germany
University of Tübingen, Department of Geosciences, Hölderlinstrasse 12, D-72074 Tübingen, Germany


in Rev. Palaeobot. Palynol. – 206: 1– 9 – DOI: 10.1016/j.revpalbo.2014.03.001 –


Stomatal data of Platanus neptuni leaves were used as CO2 proxy for the Oligocene.

CO2 calculation was based on a gas exchange model.

The data indicate quite a constant level of about 400 ppm throughout the Oligocene.


Platanus neptuni (Ettingshausen) Bůžek, Holý and Kvaček is a deciduous and preferentially azonal taxon of temperate to warm-temperate vegetation in Europe from the Late Eocene to the Late Miocene. The high fossilization potential of its leaves and easily identifiable stomata and epidermal cells make P. neptuni an excellent source of stomatal data that can be utilized as a CO2proxy. Moreover, it was found in former studies that CO2 data based on stomatal frequency data of P. neptuni overlapped to a high degree with CO2 results which are provided by other, contemporaneous taxa. In this study, the stomatal CO2 signal of P. neptuni is expanded to include the early Oligocene and is analyzed in more detail with three aims: 1) to evaluate the CO2 signal of P. neptuni stomatal data, 2) to check SI and SD data of P. neptuni for consistency, and 3) to contribute additional terrestrial CO2 data to the Oligocene record. During the Oligocene, full scale Antarctic glaciation occurred, punctuated by various distinct glaciation events. There is evidence that Oligocene glaciation was coupled to atmospheric CO2 level. Presently, the main proxy sources for Oligocene CO2 levels are alkenones and boron-isotope data, both obtained from marine sediments.

Since P. neptuni is an extinct taxon, CO2 was reconstructed by using an ecophysiological modeling approach to plant gas exchange which utilizes various other data in addition to stomatal density. Material was considered from sites which are dated to the following time intervals: early Oligocene — 33.9 to 32 Ma, late Oligocene — 27 to 26.2 Ma and 25.3 to 23 Ma, and latest Oligocene — around 24 Ma. Comparison of raw SI and SD data of P. neptuni revealed partially conflicting results, with the SD data indicating a decrease in CO2from the early to the late Oligocene whereas SI data indicate an increase. In contrast, CO2 results calculated with the gas exchange model indicate relatively stable CO2 for the considered time intervals, with levels of about 400 ppm. The reconstructed CO2 data points are similar to other proxy data and are consistent with the general climate development during the Oligocene.

Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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