Background
Anthropogenic greenhouse-gas emissions and land-surface change are profoundly altering Earth’s climate. Understanding the consequences of future warming benefits from comparison with periods in Earth history that had climate states warmer than present day.
Fossil leaf cuticles offer a terrestrial archive for palaeoatmospheric CO2 reconstruction. The frequency of stomata, the microscopic pores through which leaves exchange gases with the atmosphere often responds inversely to atmospheric CO2 and can therefore be used as empirical or process-informed proxy for past CO2.
Aim of the project
This project aims to contribute to reconstructions of Miocene atmospheric CO2 and to assess its relationship with contemporaneous palaeoclimate fluctuations. The work will focus on modern, historical-herbarium, and fossil laurel leaves. By comparing cuticula morphology across living, historical, and fossil material, the project will evaluate the potential and limitations of stomatal frequency as a palaeo-CO2 proxy.
Possible research questions:
- How do stomatal density, stomatal index, epidermal-cell density, and stomatal size vary among modern and historical laurel leaves?
- Can a reliable calibration between stomatal frequency and atmospheric CO2 be developed for the selected taxon or group?
- How comparable are fossil and modern leaf cuticles in their anatomical characteristics?
- Which sources of uncertainty arise from taxonomy, preservation, within-leaf variation, environmental effects, and calibration choice?
- How do stomatal-frequency-based CO_2estimates compare with independent marine geochemical or other terrestrial proxy records?
- To what extent can stomatal frequency provide constraints on CO2 changes during the past 50 million years (or beyond)?
Methods
The project will involve quantitative analysis of modern, historical, and fossil leaf cuticles. Methods may include: light microscopy and UV-fluorescence microscopy, scanning electron microscopy (SEM); morphometric measurements of epidermal-cell density, stomatal density, stomatal index, and stomatal dimensions; carbon-isotope analysis of plant tissue. comparison of morphological and carbon isotope data from living, herbarium, and fossil material; statistical evaluation of stomatal-frequency–CO2 relationships and associated uncertainty;
Optional fieldwork or visits to natural history museums may be possible to obtain additional herbarium and fossil cuticle material.