Molecular and isotopic proxies

The Leaf Wax Lab

The Feakins Leaf Wax Lab focuses on compound specific carbon and hydrogen isotopic analyses of biomarkers for terrestrial vegetation. Biomarkers are molecules that can be attributed to a particular organism or group of organisms. We focus on biomarkers for terrestrial vegetation in particular the plant leaf waxes. These can be analyzed by gas chromatography isotope ratio mass spectrometry and are well preserved in the geological record. We seek to establish modern calibrations as well as apply these tools to paleoclimate reconstructions, deep in geological time.

Drought tolerance in crops

In a new collaboration with Texas A&M we are exploring the development of drought tolerance in agricultural crops and using agricultural field-experiment to test theories about plant wax function and climate response.

Tropical rainforests and cloud forests

Our lab is deeply entrenched in a transect from the cloud forests of the high Andes down to the lowland tropical rainforest within Peru. We have joined forces with the the CHAMBASA project and other members of the ABERG team to generate an unprecedented leaf wax calibration study fully embedded in an ecological survey (Feakins et al., 2016a GCA, 2016b OG, Wu et al., 2017 GCA). We have soil and river studies in the same region too.

Understanding transport pathways

A major unknown is in the pathway between plant and sediment. How does sourcing vary across landscapes and how do transport processes modulate the signals of past environments captured in sedimentary archives. We are working to understand these processes in the Andes in the Madre de Dios catchment using leaf wax hydrogen isotopes (Ponton et al., 2014), carbon isotopes, lignin (Feng et al., 2016) and GDGTs, with students and collaborators.

Proxy development: leaf wax hydrogen isotopes

The Feakins Leaf Wax Lab is located in subtropical, southern California. Bathed in sunshine but short on water, we have been developing the understanding of the hydrogen isotopic signals preserved in plant biomarkers, particularly in arid regions, with a view to reconstructing climate variability and understanding arid environments around the world. We are now moving out of the subtropics into the tropics to push forward our understanding of hydrogen isotope systematics there. see publications

Hydrogen isotopes, past climates and the water cycle

Hydrogen isotopes in plant leaf waxes have the potential to record variations in water isotopes in the hydrological cycle, tracers ideal for tracking changes in global and regional circulation and the patterns of precipitation which are some of the most important aspects of climate change since water exerts strong feedbacks on the climate system and is essential for life. Leaf wax hydrogen isotope reconstructions of hydroclimate changes find global applications including Antarctica (Feakins et al., 2012), Africa (Feakins, 2013), California (Feakins et al., 2014), Asia (Aichner et al., 2015, Sharifi et al., 2015). see publications and press

Carbon isotopes and photosynthesis pathway

Carbon isotopes are a powerful tool to analyze plant photosynthetic strategies (C3, C4 and CAM) that are sensitive to climate change. Their changing proportion through time reveals insights into aridity, carbon dioxide levels in the atmosphere and temperature. In a recent paper we explore the leaf wax evidence for the expansion of the C4 pathway over 12 million years (Feakins et al., 2013). see publications and press

Carbon and hydrogen isotopes are particularly insightful in combination. As part of efforts to increase our understanding the hydrogen isotope signals preserved by plant leaf waxes, we are exploring the fundamentals of fractionation associated with different plant types, different environments and different metabolisms. For example we have demonstrated how CAM metabolism influences hydrogen isotope fractionation (Feakins and Sessions, 2010), and we analyzed plant type differences in a global dataset compiled from the published literature as part of a large community review (Sachse et al., 2012). Carbon and hydrogen isotopes together provide insights into climatic and vegetation changes. Paired C and H isotope reconstructions for NE Africa (Liddy et al., 2016), Indus (Liddy, 2017 PhD thesis) and Bengal Fan catchments are underway.