Large-scale developmental dynamics of northern peatlands

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.

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: 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 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.