Summary: This PhD project will lead to a step-change in our understanding of tropical peatland ecosystem function, development, and vulnerability, improving our ability to map peatland properties, and to model and predict peatland responses to climate change and anthropogenic pressures. The project will apply a “finger-printing” approach, using a novel combination of vegetation composition, biomarkers and pollen analysis, to characterise and understand the mechanisms at work in determining the functioning of present day peatland ecosystems. These fingerprints will then be used to reconstruct the long-term functional dynamics of peatlands, contributing to our understanding of, and ability to model, their role in the global carbon cycle.
Background and rationale: In the last decade there has been a rapid expansion of scientific interest in tropical peat-forming wetlands, fuelled by new discoveries in Amazonia and the Congo Basin (partly led by researchers at St Andrews [1,2,3]). Much of this research has focused on the value of the huge carbon stocks locked up in the peat – accumulations of dead plant material, built up over millennia underneath the swamp forests and fens. Urgent research is now underway to understand how to preserve these carbon stocks, and the characteristic fauna and flora of the peatlands, in the face of expanding human pressures, with a focus on mapping the present distribution of peat and modelling its response to 21st century climate change. But our scientific understanding of these newly recognized ecosystems and the mechanisms behind their vulnerabilities and, importantly, how to recognise long-term historical changes in these ecosystems, is still at an early stage.
Peatlands are highly structured ecosystems which form strong geographical (spatial) and developmental (temporal) patterns. Typically, a peatland may begin with a lake, such as an abandoned river channel, which progressively fills in with plant litter and sediment, laterally as well as vertically. Over centuries or millennia, a succession of different vegetational communities colonizes different parts of the site as physical and chemical conditions change [4,5]. External changes can also cause shifts in peatland ecosystem function; changes in climate, fluvial dynamics, drainage, felling and burning, can all cause changes in the physical and chemical balance which allows peatlands to function as active carbon stores and sinks.
For more than a decade, our team has been describing these patterns in Amazonian peatlands in space (using vegetation census plots and remote sensing) and in time (by analysing the sub-fossil pollen grains preserved in the peat itself as it accumulates), allowing us to map and quantify the peatland carbon store and understand how it has changed over time. More recently, we have begun research on the potential of biogeochemical markers (biomarkers) as indicators of fine-scale peatland processes . The discovery of clear process indicators would open up the possibility of rapidly assessing aspects of peatland function at lots of sites across the basin and beyond, making it feasible to scale up measurements which are currently slow to carry out. Pilot work on peat in the Pastaza-Maranon Basin (PMFB) in Peruvian Amazonia, has revealed associations between particular suites of biomarkers and key functional characteristics of these peatlands (for example, substrate oxygen levels, methane production, vegetation type, and water table fluctuation) . The proposed project will test a selection of these initial observations, systematically identifying relationships between the chosen biomarkers and peatland functional properties, with particular focus on the mechanisms behind peatland vulnerabilities. For example, methanogens are less abundant where Mauritia flexuosa palms are present because they increase oxygen levels in the surface peat, raising the possibility that felling the palms will increase methane production.
Project overview: The proposed project aims to apply a fingerprinting approach to characterising, and understanding the processes operating within, peatland ecosystems. The potential of three measurable characteristics (vegetation composition, biomarker signatures, and palynological assemblages) to be developed into proxy indicators of key peatland functions will be assessed, then applied down-core to understand how peatland function develops over millennial timescales. The ultimate aim is to provide a stronger foundation for understanding the mechanisms underlying important functional properties, such as carbon storage and biodiversity, opening the way for more insightful interpretation of remote-sensing data and better process-based peatland development models, which in turn will inform conservation and management.
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IMG_5874.JPG: “Mauritia flexuosa growing in a peatland palm swamp in Peruvian Amzonia.” Reproduced with kind permission of Dr Lydia Cole, University of St Andrews.
IMG_5702.JPG: “After field work in a swamp, the washing.” Reproduced with kind permission of Dr Lydia Cole, University of St Andrews.
IMG_5765.JPG: “Transport to an Amazon peatland field site.” Reproduced with kind permission of Dr Lydia Cole, University of St Andrews.