Net ecosystem exchange from two formerly afforested peatlands undergoing restoration in the Flow Country of northern Scotland

Northern peatlands are important in the global carbon (C) cycle as they help regulate local, regional and global C budgets through high atmospheric carbon dioxide (CO2) uptake and low net CO2 losses to the atmosphere. Since the 1900s (but particularly the 1950s) land-use change has affected many peatland areas, driven in part by attempts to improve their commercial value. During this period, many peatlands in the UK were drained and planted with non-native conifer plantations. Efforts are now underway to restore the ecosystem functioning of these peatlands to those characteristic of pristine peatlands, in particular C flux dynamics. A lack of ecosystem level measurements means that the timescales of restoration and the degree to which they are successful remains poorly determined. In this research, we present the first year-round study of net ecosystem CO2 exchange (NEE) from peatlands undergoing restoration from forestry. Annual NEE was measured from two sites between March 2014 and June 2015, where restoration commenced 10 years and 16 years prior to the start of this study, and the results were then compared to existing measurements from a near-pristine peatland. Existing NEE data (expressed as CO2-C) from the near-pristine peatland indicated a C sink of 114 g m-2 yr-1, and our estimates suggest that the older restored site (16 years) was also a NEE sink (71 g m-2 yr-1). In contrast, the younger site (10 years) was a NEE source (80 g m-2 yr-1). We critically assess the confidence of these measurements and also present these data in relation to other northern hemisphere peatlands to better understand the timeframe in which a peatland site can turn from a C source to a C sink after restoration.