Sphagnum Regeneration on Bare Peat Surfaces: Field and Greenhouse Experiments

Abstract

The re-establishment of Sphagnum mosses on bare peat surfaces is one of the main challenges faced in the restoration of post-harvested peatlands. One suggested approach to ensure moss recolonization is to use fragments of Sphagnum plants collected from a natural area as diaspores. The regeneration and recolonization potential of fragments of different species of Sphagnum were tested on bare peat, both in the field and in a greenhouse. We examined how diaspore size, density and depth of origin influence recolonization and re-establishment success. The greenhouse experiment also tested the impact of water level on Sphagnum regeneration and recolonization. Field and laboratory experiments showed that only the surface layer (0-10 cm) of a peat profile contained enough viable material to be of practical use as a source of diaspores. Small (0.5-cm), medium (1-cm) or large (2-cm) diaspores had similar recolonization success. Obtaining a precise and even size of fragments will not, therefore, be an important aspect to consider when scaling up to the quantities needed for restoring large surfaces. Greenhouse experiments showed that water level in the peat column greatly influences the recolonization success of Sphagnum diaspores. Most species reacted positively to wetter conditions, with the notable exception of S. fuscum. A density of 450 Sphagnum plants per m 2 resulted in some Sphagnum species covering up to 50% of the peat surface in 3 months and 100% in 6 months, when the water table was close to the peat surface in the greenhouse experiment. Sphagnum cover reached 5-10% after 3 mqnths in the drier treatments of the greenhouse experiment and was generally comparable to the results obtained in the field after one season of growth under shade cloth. Improving the humidity conditions offered to diaspores is by far the most promising approach to reduce the quantity of diaspores needed to re-establish a significant moss cover rapidly on a post-harvested surface. The selection of appropriate species and densities according to the dryness of the surface to be restored are two other elements to consider in minimizing the amount of source material needed for restoration.