PeatCHEM · Quantifying peatland pH across past periods of natural climate change using lipid biomarkers

Peatlands play a major role in the global carbon cycle storing around 25% of all soil carbon and being the largest natural source of methane to the atmosphere. Their future carbon (and other nutrient) dynamics are poorly constrained given the many environmental and biotic variables affecting them. A crucial parameter, controlling peatlands carbon storage and methane emissions is pH, which is closely related to vegetation and microbial community dynamics. Long term pH measurements are limited to at most a few years to decades, limiting our understanding of the long-term consequences of climate change on peatland pH and hence peatland carbon cycle dynamics. The PeatCHEM project will dramatically change our understanding of the response of peatland pH to long-term environmental change. I will quantify peatland pH across the last 68 million years (Cenozoic), a period characterized by major climatic and evolutionary change, using a unique database of over >450 lignites (fossilised peat) from all over the world. Peatland pH will be quantified using two pH proxies that were recently developed at the University of Bristol based on two distinct family of lipid biomarkers: branched glycerol dialkyl glycerol tetraethers (brGDGTs) and hopanes and complemented by vegetation and temperature reconstructions based on n-alkanes, triterpenoids and brGDGTs. This project will identify the main parameters controlling pH variations in peatlands and ascertain the impact of both abrupt and long-term climatic and ecological changes across the Cenozoic on peatland pH. I will constrain the response of peatlands pH to major climatic events such as the Paleocene- Eocene Thermal Maximum (PETM) and the Eocene Oligocene transition (EOT). This project will produce an unprecedented database of peatland pH covering a large range of environmental settings that will revolutionise our understanding of the vulnerability of peatlands to climate and environmental change.