Large-scale developmental dynamics of northern peatlands
Project description
Peatlands are terrestrial wetlands in which saturated soil conditions prevent the complete decomposition of plant litter, causing carbon-rich peat to accumulate at the Earth’s surface. Since the Last Glacial Maximum, approximately 21,000 years before present, peatlands have spread slowly but persistently across deglaciated areas of the northern hemisphere, and now contain up to one third of all global soil carbon. However, peatland carbon budgets are sensitive to changes in climate and land use, and are also susceptible to wildfire. Furthermore, important aspects of the initiation, development and fire regimes of peatlands remain poorly understood, areas that this project will explore.
Previous research by the supervision team (Morris et al., 2018) has shown that the initiation of peatlands after the retreat of glacial ice was driven primarily by warming growing seasons, allowing communities of peatland plants to begin to establish in inundated areas of postglacial landscapes. However, the response of peat initiation to warming is complex and varies between regions, indicating that mechanisms other than climate also play an important role (Gorham et al., 2004). This project will unpick this question by examining basal sediments and peat layers to discern the mechanisms through which peatlands established in different areas (e.g., terrestrialisation of postglacial water bodies, paludification of existing terrestrial forests and tundra, or peat formation directly onto bedrock), which seems likely to explain regional differences. The answer to this question will also contribute to an improved understanding of the likely fate of currently deglaciating landscapes such as retreating mountain glaciers, where moss banks are beginning to develop into nascent peatlands which may represent important carbon sinks, and water resources, of the future.
Peatlands often initiate as fens: wet, nutrient-rich, high-pH, biodiverse ecosystems that receive water and nutrients from the surrounding landscape. Once sufficient peat has accumulated, the growing surface rises above surrounding hydrological influences, at which point the sole source of water becomes precipitation and the peatland is said to have become a bog. This leads to a sharp decline in pH, nutrient levels and biodiversity, and important changes in peatland carbon gas fluxes. Previous research (e.g., Väliranta et al., 2010) has suggested that climate is the main driver of fen-bog transitions, but preliminary work by the supervision team indicates that other factors, such as topographic position and peatland age, are more important. This project will seek to shed light on the controls on trophic changes in peatlands.
In some regions with continental climates, wildfire is a natural part of peatland ecosystem development. Fire regimes in peatlands, particularly their links to climate, are complex, and their drivers are not fully understood (Sim et al., 2023). Macrocharcoal records from peat cores offer the opportunity to reconstruct the frequency and severity of past fire regimes, while testate amoeba analysis allows the reconstruction of long-term changes in palaeohydrological conditions. This project will link these two proxies to provide new insights into the climatic and hydrological controls on long-term changes in peatland palaeo-fire regimes.
The project will address three primary aims, each of which can be tailored to the interests and strengths of the student:
- Establish the links between climate warming, and the timing and mechanisms of peat initiation.
- Explore the respective roles of climate and landscape characteristics in driving the fen-bog transition.
- Examine in detail long-term palaeo-fire and palaeohydrological regimes at one or more individual peatland sites, and the links between these.
The three aims will form the basis of thesis chapters, as well as articles for major, international journals, which the student will write under the guidance of the supervisors.
The project will use a powerful and novel combination of palaeoecological reconstruction techniques in detailed, site-specific studies, including Fourier-Transformed infrared (FTIR) spectroscopy of sub-fossil charcoal, palaeo-hydrological reconstruction from testate amoeba analysis, plant macrofossil analysis, and peat geochemical analysis; and modelling and meta-analysis techniques to extend inferences to larger spatial scales. Core collection will also involve extended fieldwork in the Arctic, sub-Arctic or Boreal zones.
Candidate profile
The student should have a keen interest in environmental change and palaeo-environmental reconstruction, and a strong background in Earth sciences, environmental sciences, plant sciences, physical geography, or a related discipline. The candidate should also have demonstrable skills in microscopy and palaeoenvironmental techniques (in particular, experience with charcoal analysis, such as FTIR spectroscopy, would be an advantage). Candidates should be proficient in data handling, numerical methods and the R programming language. Excellent scientific writing and communication skills are essential. Students should have the ability to work independently, showing initiative, while also being open to collaboration with colleagues. Experience in the field (specifically Arctic/Boreal ecosystems) is desirable but not required.
Training
The student will work under the supervision of Dr. Paul Morris and Dr. Liam Taylor in the School of Geography, where they will become a member of the River Basins Processes and Management research cluster. The project will provide the student with high-level training in (i) peatland science; (ii) Quaternary climate and environmental change; (iii) palaeoenvironmental analysis; (iv) advanced skills in data handling and numerical methods; and (v) scientific writing and communication. The student will be supported throughout by a comprehensive PGR skills training programme that will focus on developing knowledge and intellectual abilities; personal effectiveness; research governance and organisation; and engagement, influence and impact. Training needs will be assessed at the beginning of the project and at key stages throughout the project and the student will be encouraged to participate in the numerous training and development course that are run within the university to support PGR students, including statistics training (e.g. R, SPSS), academic writing skills, grant writing etc. Supervision will involve regular meetings with all supervisors, and additional guidance from a research support group.
References
Gorham E, et al. (2007) Long-term carbon sequestration in North American peatlands. Quaternary Science Reviews, 26, 300–311.
Morris PJ, et al. (2018) Global peatland initiation driven by regionally asynchronous warming. Proceedings of the National Academy of Sciences, 115: 4,851–4,856.
Sim et al. (2023) Regional variability in peatland burning at mid-to high-latitudes during the Holocene. Quaternary Science Reviews, 305, 108020.
Väliranta M, et al. (2017) Holocene fen-bog transitions, current status in Finland and future perspectives. The Holocene, 27, 752-764.