PhD: The palaeoecology of leaf chemistry

The epicuticular leaf waxes of terrestrial plants are in part composed of long chain normal alkanes (n-alkanes), which are resistant to decomposition and commonly used biomarkers in palaeontological investigations (e.g. Schellekens & Buurman, 2011). Numerous studies have investigated variation of these biomarkers in many plant species (Bush & McInerney, 2013), but the likelihood of variation of n-alkanes and other plant leaf chemical markers (e.g. secondary metabolites, fatty acids from leaf waxes etc) driven by temperature, precipitation or other environmental variables has received little attention. Additionally, the utility of leaf chemistry to investigate plant response to environmental change in the Quaternary has not been fully investigated (Haggi et al., 2014).
The aim of this project is to determine baseline leaf chemistry data for a range of living fossil and native UK species and investigate how these species respond to changing environmental conditions along natural climate gradients. Selected taxa will also be used to investigate their response to experimental treatments e.g. temperature change, water availability variation, CO2 level. Leaf chemistry will be compared to other leaf traits (e.g. leaf mass per area, C:N ratios etc) to determine if variations in leaf chemistry co-vary with other traits known to respond to various environmental pressures (e.g Bacon et al., 2015; Wright et al., 2004). The project will also investigate leaf chemistry markers and variations in a range of Holocene sediment and peat cores from arctic, temperate and tropical sites to determine if and how leaf chemistry tracks environmental change in these different locations over long timescales.

In this project, you will work with scientists at the University of Leeds and in botanic gardens around the UK to quantify leaf chemistry changes to temperature/precipitation gradients and to understand how these signals can be used to interpret palaeoecology.
In particular, according to your particular research interests, the studentship could involve
Determining base-line leaf chemistry data for “living fossil” taxa that have previously not been fully investigated
Evaluating the changes in leaf chemistry of selected taxa along climate gradients with a particular focus on “living fossil“ taxa, e.g. Gingko biloba, Araucaria araucana etc
Compare leaf chemistry data to other leaf traits associated with plant responses to environmental change (e.g. leaf mass per area, stomatal size and number, carbon:nitrogen uptake etc)
Conduct experiments to determine the effects of environmental variables, for example temperature, water availability, CO2 etc, on leaf chemistry and the production of secondary metabolites.
Investigate the leaf chemistry signal and its utility as a palaeoecological tool in a range of Holocene sediment and peat cores from arctic, temperate and tropical biomes form a large collection housed in the School of Geography.

References:
Bacon et al., (2015) Can atmospheric composition influence plant fossil preservation via changes in leaf mas per area? A new hypothesis based on simulated palaeoatmosphere experiments. Palaeogeography, Palaeoclimatology, Palaeoecology
Bush and McInerney (2013) Leaf wax n-alkane distribution in and across modern plants: Implications for palaeoecology and chemotaxonomy. Geochimica et Cosmochimica Acta 117: 161 – 179
Diefendorf et al., (2011) Production of n-alkyl lipids in living plants and implication for the geologica past Geochimica et Cosmochimica Acta 75: 7472 - 7485
Haggi et al., (2014) On the stratigraphic integrity of leaf-wax biomarkers in loess paleosols. Biogeosciences. 11: 2455 – 2463.
McInerney & Wing (2011) The Palaeocene-Eocene Thermal Maximum: a perturbation of carbon cycle, climate and biosphere with implications for the future. Annual Review of Earth and Planetary Science 39: 489 – 516
Schellekens & Buurman (2011) n –Alkane distributions as palaeoclimatic proxies in ombrotrophic peat: The roleof decomposition and dominant vegetation. Geoderma 164: 112
Wright et al., (2004). The worldwide leaf economic spectrum. Nature. 428: 821–827.