Insights on carbon dioxide and methane fluxes from natural peatland pools in Flow Country blanket bogs

Abstract

The important role of small waterbodies within the global carbon cycle has become increasingly recognised in recent years, as has the role of peatland ecosystems in regulating global carbon emissions. As a result of the high water table required for the proper functioning of a healthy peatland, freshwater pools are a common feature on the peatland surface, and these microforms are particularly common in northern peatland settings, often forming complex, patterned arrangements on the peatland surface, referred to as pool systems. Existing research suggest that these pools are a source of carbon to the atmosphere, particularly through the release of greenhouse gases in the form of
carbon dioxide and methane, and they have the potential to be important in signalling changes to the peatland environment in a changing climate. However, while some research has looked at peatland pools (and other similar small waterbodies), few have looked specifically at the context of pools within a temperate blanket bog and none looking at the dynamics of greenhouse gas flux from these systems.
For this thesis, carbon dioxide and methane fluxes were surveyed from a range of peatland pools situated in blanket bogs across the Flow Country of Northern Scotland, with the primary focus being on a selection of three pools at the ‘Cross Lochs’ pool system and nine pools near Loch Culaidh, both sites near to Forsinard, situated in the heart of the Flow Country UNESCO World Heritage Site. Pools were selected based on three categories defined by the size and permanence of the waterbodies: Permanent Pools, Semi-permanent pools and Sphagnum Hollows. Additional sites were surveyed at Munsary Peatlands, Caithness and near Sandwood Bay, Sutherland. The ‘Cross Lochs’ pools were the focus of a study assessing diurnal variability in water-atmosphere gas exchange from peatland pools (Chapter 2). Fieldwork at all other sites was used to investigate the longer-term temporal trends in carbon dioxide and methane fluxes from peatland pools and provide some insights into the factors influencing these trends (Chapter 3). Pulling these strands of research together and recognising the growing body of
evidence that pool systems are dynamic and evolving systems which are likely to change the implications of the water to atmosphere carbon fluxes from peatland pools at the landscape scale. Furthermore, the dataset allowed simulations for a range of scenarios to address questions of how changing pool coverage on peatlands may influence greenhouse gas emissions in this environment (Chapter 4).
Overall peatland pools were observed to be a net source of carbon to the atmosphere (1945 mg CO2eq m-2 d-1). The pools were observed to show a clear daily fluctuation in carbon dioxide flux with higher fluxes during the night than during daytime, most pronounced in Sphagnum Hollows. For logistical reasons, sampling campaigns often focus on daytime only measurements. However, based on this research, this could lead to a consistent underestimate from daytime-only flux measurements. Thus, this finding highlighted the need to account for diurnal variations when inferring carbon fluxes from daytime-only measurements. Methane flux was not found to be regulated by daily cycles but both carbon dioxide and methane fluxes were seen to respond to longer-term changes
in the pool environment. In particular methane flux was seen to be particularly influenced by periods of high water temperatures. However, a small sample size during these conditions means that a definitive understanding of this response could not be drawn from this study. Fluxes of both gases were also found to be highly influenced by pool morphology, with the smallest pools (Sphagnum Hollows) producing the highest and most variable flux estimates. This matched expectations that these shallow systems would be the most responsive to environmental changes and the findings of this study highlight the importance of sampling from a range of pool types when assessing the carbon dynamics
of peatland pools. unlikely with current climate change projections and instead it is more likely that these smallest pools will become less prevalent in future.
Overall, it was found that as climate changes it will become increasingly more important to consider pool greenhouse gas fluxes to produce accurate peatland carbon flux estimates and understand landscape-scale dynamics of both terrestrial and water dominated components of these ecosystems. However, at present and most likely in the future, emissions associated with natural pool systems are not anticipated to o[set the carbon sequestration potential of blanket bogs in the Flow Country. Future research should seek to expand our understanding of how pools process carbon and contribute to greenhouse gas emissions in the context of peatland restoration, where pools are created
rather than naturally occurring.

Datum der Bewilligung	17 Juni 2026
Originalsprache	English
Gradverleihende Hochschule	University of the Highlands and Islands
Betreuer/-in	Peter J. Gilbert (Supervisor) & Roxane Andersen (Supervisor)