Drivers of success in 53 cutover bogs restored by a moss layer transfer technique

The moss layer transfer technique has been used since the 1990s to restore bogs in North America after peat extraction. This article assesses the influence of drainage-related, peat physicochemical, meteorological, management and landscape factors on the vegetation of extracted peatlands that have been restored in this manner. It draws upon data from a unique long-term monitoring programme covering 53 restoration projects spanning 600 km across eastern Canada. The time since restoration ranged from 3 to 15 years, and the rehabilitated peatlands had on average three permanent plots where vegetation was recorded every two years. Overall, the study included 246 permanent plots and 946 observations (plots*year of survey). Redundancy and cluster analyses showed that successful restoration, defined by the dominance of a Sphagnum carpet (54% of all plots at the most recent observation), was mainly associated with effective blocking of the former secondary drainage network within the restored sector, while plots dominated by bare peat (24% of all plots) occurred more often if a hot summer followed restoration works and where higher proportions of the surrounding land were subject to peat extraction. Management decisions, such as the season when restoration work was carried out, also substantially influenced restoration outcomes. For example, restoring in spring increased the likelihood of initiating an alternative successional trajectory characterised by dominance of the pioneer moss Polytrichum strictum (22% of all plots). However, a tendency towards Sphagnum colonisation and the development of Sphagnum carpets was observed over time in practically all plots. These results will inform future restoration efforts using the moss layer transfer as a peatland restoration method.