Aqueous carbon losses from the Glenfeshie Mòine Mhór

Abstract

Healthy, functioning peatlands are a net carbon sink and are a globally important terrestrial carbon store alongside numerous other wider ecosystem benefits. Degradation of peatlands by unsustainable management and erosion can increase emissions of carbon dioxide (CO₂) and methane (CH₄). Peatlands are also a principal source for dissolved organic carbon (DOC) loss to the fluvial environment and water discolouration. Understanding of the aquatic carbon budget is important in terms of policy and anthropogenic climate change mitigation in today’s society.

The Mòine Mhór (900-950 m) is an upland blanket bog located in the north-west of the Cairngorms National Park, Scotland. It is currently in poor condition with 242 ha of bare peat located within the 1600 ha study site, equating to 15 % bare peat coverage. This study aimed to further the understanding of the variations in catchment characteristics and water chemistry between eight streams monitored on the Mòine Mhór plateau.

Through a nested design to capture data using continuous monitoring systems, grab sampling and flow monitoring, the hydrology of the peatland in relation to river flow was analysed. It was found that there were no significant differences between the monitored streams in relation to the catchment specific conditions and water chemistry parameters recorded (pH, absorbance, conductivity, dissolved oxygen and suspended sediment). Small variations were evident, such as the lower absorbance values for the Garbhlach catchments which were less eroded than the Caochan Dubh catchment. When taking into consideration all the monitored streams, a greater extent of bare peat within the catchments did not significantly correlate with the largest DOC exports. Overall, the larger stream catchment areas had higher mean DOC exports (2.7 – 2.8 gC/m²) than when compared to the values from the smaller stream catchments monitored (0.5 gC/m²). However, there was a significant positive correlation between water quality parameters and flow rates across the monitored catchments. The aquatic carbon budget at the Mòine Mhór south east tributary was quantified by use of the data collected from a spectro::lyser, which indicated a carbon export of 35.5 gC/m²/yr. Flux estimates of annual DOC export from the Mòine Mhór were 28 gC/m² which is representative of a typical peatland headwater catchment. This equates to a total carbon loss through runoff over the area of 31 tonnes of carbon per year.

The key processes affecting the aquatic carbon export from the Mòine Mhór study site were summarised in a conceptual model. The main processes related to flow pathways, seasonal climate and vegetative cover. Deer are also a large contributor to the condition of the site and require ongoing management should restoration take place at this site. The benefits associated with restoring the site include its designated status, prominent location within the Cairngorms National Park and the carbon emissions that will be saved by halting or reversing the currently eroding Mòine Mhór peatland.

Date of Award	2020
Original language	English
Awarding Institution	University of Dundee
Sponsors	Scottish Natural Heritage & Scottish Environment Protection Agency
Supervisor	Andrew Black (Supervisor), Mark Cutler (Supervisor) & Tom Ball (Supervisor)