Long-term assessment of the Moss Layer Transfer Technique for the restoration of Sphagnum-dominated peatlands

Abstract

Introduction: Peatlands are crucial for carbon storage and biodiversity but face increasing human degradation. The Moss Layer Transfer Technique (MLTT) has emerged as an effective method for restoring Sphagnum-dominated vegetation in post-extracted horticultural peatlands. Objectives: This study evaluates vegetation restoration trajectories over a 20-year period in 147 MLTT-restored sectors across Canada, compared to 227 reference sites in four climatic regions. Methods: Vegetation surveys from natural and restored peatlands were classified using Hierarchical Classification on Principal Components, identifying eight vegetation groups representing reference assemblages or successional stages. Indicator species analysis refined group characterization, and groups were allocated to four climatic regions. A state-based Ecological Quality Assessment (EQA) framework quantified convergence of restored sectors toward regional reference ecosystems. Electrical conductivity and pH were measured in water samples from the reference peatlands but in peat samples from the restored peatlands. The resulting differences were then analyzed using the Kruskal–Wallis and Dunn's tests. Results: In Eastern Canada, restored sectors progressed toward reference conditions, with integration rates from 10 to 100% depending on post-restoration age and region; notably, approximately 80% of restored peatlands in the Southern St. Lawrence region fell within the reference envelope within a decade. In Western Canada, from Manitoba to Alberta, sectors tended toward fen rather than bog references, likely due to the soil geomorphological properties of the substrate conditions. Conclusions: These results underscore the importance of assessing residual peat properties prior to MLTT application and suggest that optimizing the rewetting step can enhance Sphagnum reestablishment. Overall, MLTT effectively accelerates peatland succession, while the EQA framework proves valuable for quantifying restoration success.