Towards unravelling the peatland carbon cycle 'black box': linking peatland management, habitat status, and climate to water chemistry and quality, and greenhouse gas fluxes

UK blanket bog is a significant carbon (C) store and provider of ecosystem services, but historical mismanagement and recent climate change has led to destabilisation of soil C stocks and increased drinking water treatment costs in peatland draining catchments. To restore these services, a better understanding of the impacts of vegetation management, habitat restoration, and climate change upon peatland C cycling and water quality is required. Therefore, this thesis sought to assess the differences in C fluxes and water quality in blanket bog soils under different heather management regimes, habitat and restoration statuses, and climatic conditions.
Using a combination of field samples and a novel mesocosm experiment design, water quality and greenhouse gas fluxes were linked to heather management and peatland restoration practices and assessed alongside soil and climatic data. In-situ measurements from heather-managed blanket bog compared well with mesocosm measurements excluding methane flux. Vegetation management was beneficial for water quality but was accompanied by an increase in greenhouse gas emissions. Results indicated that the trajectory towards habitat recovery from degraded to an ‘intact’ status (i.e., functioning as a C sink) status following restoration is not straight-forward, given that there was a decline in water quality in mesocosms of recently restored habitats, likely attributed to disturbance following restoration. Water table depth decline and temperature increases associated with seasonal change led to increased dissolved organic C loading in porewaters but was accompanied by increased gaseous C uptake. Disinfectant by-products were produced following chlorination in all tested porewaters, and samples from cores dominated by vascular plants, especially Molinia had the lowest dissolved organic carbon removal rates. Therefore, it is suggested that managing heather-dominated blanket bog to maintain a desirable vegetation community composition (i.e., Sphagnum dominated) and higher water tables will increase blanket bog resilience and lower dissolved organic C concentrations. However, as higher methane emissions were associated with wetter sites, methane flux should be carefully considered as part of rewetting strategies.
This was the first study to directly assess C gaseous flux and water quality measurements from a field experiment comparing unmanaged, burnt, and cut heather-dominated blanket bog areas to paired peat mesocosms. It showed that, using a before-after-control-intervention approach, meaningful comparisons could be made between mesocosm and field measurements. Longer-term monitoring is recommended to enable better assessment of ecosystem service delivery trajectories, to help inform appropriate management and restoration practices aimed at protecting blanket bog ecosystem service provisioning in the context of unprecedented anthropogenic environmental change.