The carbon balance of gullied and hagged blanket peatlands

Peatlands are a globally important carbon store, hosting at least one third of terrestrial soil carbon. However, many of these systems have been degraded through human action. Restoration investment seeks to protect the ecosystem and carbon store and encourage enhanced carbon sequestration and minimise adverse greenhouse gas (GHG) forcing. Blanket peatlands are a type of peatland most commonly found in wet temperate oceanic climates, but are subject to much erosion if the vegetation is disturbed because they often occur on sloping terrain.

 

This PhD would investigate the carbon balance of eroded blanket peatlands where there are peat ‘haggs’ (high remnant points) surrounded by lower eroded components such as gullies. The study will examine hagged peatlands incorporating hagg top and gully bottom locations, for a range of hagg heights, in three key states: i) eroding/stable with no active restoration or ‘self-healing’; ii) managed through active peatland restoration management; iii) naturally self-healing sites where revegetation is occurring.

 

While there may be good potential for carbon accumulation in restored gully floors, this could be offset by higher methane emissions associated with ponded conditions. In addition, carbon gains in the gully bottoms may be offset by continued net losses from the haggs and larger areas between the gullies. Even after gully blocking, water tables in gullies can remain substantially below the height of the peat at the top of the haggs. Therefore it is important to understand how these systems function to inform management best practice (e.g., hagg reprofiling) and understand the GHG trajectory from degraded to fully restored peatland.

 

Measurements would include methane and carbon dioxide fluxes using a field portable gas analyser, water-table depth, vegetation, and surface ponding area. Fluxes would be determined for pooled and non-pooled sections of gullies and the surrounding haggs (chosen to range in size from a few metres to tens of metres across) that lie between the gullies. DEMs and vegetation classifications would be derived by drone survey with some ground truthing. These data would be input into the DigiBog_Hydro model to help understand how different geomorphological components influence water-table dynamics. The interactions between dominant vegetation type and water-table depth on the carbon balance could also be tested via field and laboratory experiments. A range of sites would be included in the study to capture different environmental (e.g. climate, rainfall chemistry) conditions and dominant vegetation.

 

The student would spend some time with the CASE partner, Natural England. Working with Natural England will enhance the practical elements of the project and provide training for the student in skills including policy development and condition assessments. Here are some examples of benefits derived from working on a PhD with Natural England as a CASE partner: https://naturalengland.blog.gov.uk/2019/06/18/developing-the-environmental-scientists-of-the-future/