Towards the regeneration of brown mosses for fen restoration

Abstract. A low rate of establishment in brown mosses is generally observed following large-scale restoration of fens. As brown mosses are important components in peat accumulation in fens, their low recovery rate has been a concern in the past decade. It was suggested that the restoration method used for bogs, the Moss Layer Transfer Technique (MLTT) should be adapted for fen restoration by identifying factors limiting the establishment and recovery of brown mosses. In this study, we evaluated the regeneration potential of four common brown mosses, Aulacomnium palustre, Campylium stellatum, Scorpidium cossonii and Tomentypnum nitens, according to three factors that can have an impact during restoration: 1) distance of the fragment below the moss apex, 2) mechanical fragmentation of mosses, and 3) enhanced nutrient availability, and this, in growth chambers (within Petri dishes) and field experiments. Under controlled conditions, similar results were obtained for all four brown mosses studied: the severe fragmentation of mosses most drastically improved their regeneration potential. Phosphate fertilization, even at the lowest dose, increased moss regeneration, and brown mosses showed higher recovery in the first 3 cm below the apex. Liming only improved the regeneration of C. stellatum. However, unclear, and even contradicting results were obtained when treatments were applied in the field, where an overall very low establishment of brown mosses was observed in response to the rather prevailing adverse environmental conditions (e.g., erosion, frost heaving, low water table level). The direct application of some of our results into an adapted version of MLTT might be challenging, as it may require a certain level of meticulosity that large-scale mechanical fen restoration cannot provide.