Managing Peatlands as Carbon Stores

Peatlands comprise a large accumulation of terrestrial organic matter, fixed from the atmosphere by photosynthesis, and are, therefore, important carbon stores. However, many peatlands in the UK have suffered from disturbance, including drainage, agricultural improvement, peat cutting, afforestation, burning, and increased atmospheric nutrient deposition. Such disturbance has altered peatland carbon cycling processes and has led to increased release of the soil carbon stock to the atmosphere. Therefore, protection and restoration of these degraded peatlands is being pursued by national and regional agencies in order to conserve existing carbon stocks (to help mitigate climate change), and to protect wildlife habitats and landscapes. Restoration usually involves blocking of drainage ditches to raise the water table and hence encourage waterlogged conditions that will enable peat to form again. It is believed that restoration reduces carbon losses both to the atmosphere and the aqueous environment. However, it may lead to an increase in methane (CH4) emissions, at least in the short term, which is a more potent greenhouse gas than carbon dioxide (CO2). Increases in CH4 emissions may reduce or even outweigh carbon savings associated with peatland restoration, when the carbon balance of a peatland is expressed in terms of global warming potential (GWP). Although there is some evidence that restored peatlands emit much less CO2 than degraded peatlands, there is considerable uncertainty over whether or not restored peatlands become carbon sinks in GWP terms because they are thought to emit more CH4. In addition, aqueous fluxes of carbon from peatlands are rarely, if ever, considered as part of the peatland carbon budget. Quantification of aqueous carbon loss, in addition to gaseous carbon losses, from peatlands is, therefore, critical in determining carbon budgets for sites, and in understanding the potential of restoration to reduce carbon losses and green house gas (GHG) flux. This project will address this knowledge gap by investigating how restoration affects the carbon sink function of ombrotrophic bogs. The research will take place at Thorne and Hatfield Moors, where existing restoration schemes, monitoring programmes, data sets, and management and academic help from Natural England are available. In particular the research will (i) investigate the impact of (a) water table height, (b) sedges and (c) time since restoration on CH4 emissions and GWP and (ii) elucidate the processes and factors that account for the high rates of CH4 emitted from blocked drainage ditches. The project will deliver new insights into how restoration practices influence the carbon budget and GWP of peatlands and the results will be used to improve UK and international policy and guidelines on peatland restoration and management for climate mitigation. It will provide an excellent package for student training, incorporating elements of field and laboratory work, enabling the development of a broad technical skills base, and peatland management. The inter-disciplinary nature of this project will provide the student with skills that will be of great value to their future scientific career. The fieldwork will build on an existing soil and soil water monitoring programme installed as part of a previous PhD project supervised by Chapman. Therefore, we are confident that the project is suitable for PhD study and that our expectations of the student are appropriate. Chapman and Baird have an excellent track record of PhD supervision and project completion, with students going on to successful post-PhD careers. The partnership between Leeds and the CASE partner, Natural England, will provide strength and depth across the inter-disciplinary topics of the project, in particular, peatland ecology, hydrology, soil science, carbon cycling and peatland management.