Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

When abandoned peatlands undergo restoration following the extraction of peat moss, newly reintroduced diaspores may be buried by particles eroded from the stripped peat (decomposed) or from adjacent extraction activities. This study examined, in the greenhouse, the tolerance of six species of peat mosses to burial by peat. One of the experiments consisted of depositing predetermined thicknesses (0, 10, and 30 mm) of peat onto partially established mats of Sphagnum species and true mosses. A second experiment evaluated the effect of a wider range of burial depths (maximum set at 40 mm) on Sphagnum fuscum. After ten weeks of burial, the expansion of the established mosses buried under 10 mm of peat was slowed down but not arrested. Dicranella cerviculata is the only species that did not tolerate being buried. The mosses showed three types of final responses to burial: neutral, in which the increases and decreases in cover were not significantly different between the tested and the control depths (for Sphagnum fuscum buried under 5 mm and Sphagnum fallax buried under 10 mm); negative, in which the decrease in cover was significant at the depth tested (for Sphagnum fuscum, Sphagnum magellanicum, Polytrichum strictum, and Dicranella cerviculata buried under 10 mm or more, and for Sphagnum fallax and Sphagnum capillifolium buried under 30 mm of peat); and positive, in which the increase in cover was significant at the depth tested (for Sphagnum capillifolium buried under 10 mm of peat). After burial, mosses emerged by means of an innovation or a continuity of the stem of the initial individual for the Sphagnum species, and by means of an innovation growing out of the apex of buried individuals in the case of Polytrichum strictum. It appears that restoration efforts may be futile in cases where diaspores and newly established mats are likely to be buried at depths exceeding 10 mm.