Oligocene – Miocene palaeoatmospheric CO2 concentrations reconstruction based on stomata frequency analysis of fossil leaf remains

Background and aim of the research:
Anthropogenic greenhouse gas emissions and modification of land surfaces are changing Earth’s climate profoundly. IPCC assessments indicate that global temperature will rise by about 3 °C during the next decades and will turn the present day “icehouse climate” into a “greenhouse climate”.

In order to assess the human impact against the natural climate variability, studies of past warm intervals are of pivotal importance. The Miocene is of particular interest for palaeoclimate studies as it represents a period of the Cenozoic which is characterized by extreme climate states such as the Middle Miocene climatic optimum and two major glaciations during the Early and the late Middle Miocene, when the east Antarctic ice sheet was established. In addition to the marine geochemical proxy records, the pore (stomata) frequency, preserved on the cuticle of fossil leaf remains, represents a terrestrial proxy for atmospheric CO2 that is based on the inverse relationship between atmospheric CO2 and the number of stomata. It provides a robust method for estimating CO2 levels for short and geologically long-time scales.

Because the stomatal frequency response to CO2 is species-specific, quantitative estimates of CO2 are limited to extant species. This method requires good preservation of leaf fossils with cuticles and a good understanding of taxonomy and evolution of those elements that are followed. The present project is focusing on modern and fossil, Oligocene and Miocene laurel leaves.

The study involves quantitative cuticle analysis with different microscopic techniques and computer aided image analysis of modern (living) and historical herbarium leaves as far as back in time to the 17th century.

The goal of this project is to contribute to the reconstruction of Cenozoic palaeoatmospheric CO2 levels and asses its impact on concomitant palaeoclimate fluctuations.  

Research methodologies and database:
Laboratory preparation techniques of modern and fossil leaf cuticles, light microscopy and UV-fluorescence microscopy, SEM, Image analysis, eventually C-isotope analysis or FTIR-microscopy.

Learning outcomes:
The student will work on morphometric analysis of epidermal cell parameters (epidermal cell density, stomata density, stomata size) of modern and historical cuticle material and the comparison with those of fossil leaf remains. The student will learn modern microscope techniques and the use of image analysis programs. Additional fieldwork or study visits in Natural History Musea to collect herbarium and / or fossil cuticle material is optional. A background / interest of the candidate in botany is an advantage.  

Picture 1: living Cinnamomum tree (by Poyt448 Peter Woodard - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=9979645)
Picture 2: herbarium leaf of Cinnamomum triplinerve FMB-102726, Nombre científico: Cinnamomum triplinerve Identificado por: País: Colombia Departamento: Risaralda, Municipio: Balboa
Picture 3: fossil leaf remain of Cinnamomum / Laurophyllum from http://www.biolib.cz.  
Picture 4: cuticle of fossil Cinnamomum leaf remain (Daphnogene cinnamomea) from Oligocene  sediments, Czech republic (collection Z. Kvacek, Charles University of Prague)  


Published June 5, 2018 4:09 PM - Last modified June 5, 2018 4:09 PM

Scope (credits)