Growth potential of three Sphagnum species in relation to water table level and peat properties with implications for their restoration in cut-over bogs

1. Growth in length and weight of three species of Sphagnum (S. fuscum, S. magellanicum and S. fallax) was studied in a glasshouse experiment. The Sphagnum mosses were cultivated at natural density on cores of five different peat types, representing a gradient of increasing disturbance. Two water levels were controlled and maintained to simulate natural and drained situations. 2. Significant differences in the growth of the three Sphagnum species were observed. Canonical multivariate analyses showed decreasing influence by explanatory variables in the order: species > water level > peat-type. 3. S. fallax was more sensitive both to water table depth and to peat properties. Yet, in the Swiss Jura Mountains, it is the most widespread species in paludification processes of drained bogs after the cessation of peat mining or harvesting. This apparent paradox is discussed. 4. Feat type was influential only when the water table was maintained at a low level (-40 cm), simulating drained conditions. Results of analyses taking into account peat physical and chemical properties show that drained sites undergo a strong chemical disturbance, which, in turn, affects the growth of Sphagnum mosses. However, depending on the evolution of the peat, a particular combination of chemical and physical properties may favour the growth of Sphagnum mosses even at a low water table. 5. In setting priorities for bog restoration, S. fallax should be favoured as a pioneer to stimulate a rapid colonization and recovery of Sphagnum lawns on which other species, more characteristic of the ombrotrophic bog environment, can re-establish.