Assessing the impact of rehabilitation and inter-annual climatic variability on the net ecosystem carbon dynamics of raised bogs in Ireland.

In Ireland, peatland ecosystems cover ~20% of the land area and hold up to 75% of the soil organic carbon stock, however over 90% of these systems have been degraded due to activities such as agriculture, forestry and extraction for horticulture or energy. Due to their climate mitigation potential the rehabilitation of these systems through rewetting forms an integral part of the national climate mitigation strategy in Ireland. A key aspect of this land use policy is the rehabilitation of ~33,000 hectares of former industrially extracted peatlands through rewetting/water table management. The success of these rehabilitation activities are dependent however on maintaining the hydrological integrity of these sites, which are susceptible to inter-annual variation in climate, such as changes in precipitation and temperature. This study utilised eddy covariance techniques to assess ecosystem to atmosphere dynamics of carbon exchange at two sites, a remnant raised bog ecosystem with five site years of data that was operational during two exceptionally dry climatic years (2018 and 2021), and a former industrial cutaway site where the drains were blocked and the water table raised in  2015. This work provides insight into the vulnerability and resilience of raised bog systems to inter-annual climatic variability and will explore the impacts of the magnitude and duration of reductions in water table height and elevated winter temperatures on both Gross Primary Productivity and Ecosystem respiration. The work also provides further insight into the time dependent impacts and potential emissions savings of peatland rehabilitation as the former cutaway sites undergo both hydrological and ecological transitions.