Bryophyte community structure in a high boreal poor fen in northern Alberta, Canada

The underlying mechanisms behind the distribution of four focal bryophytes was examined in a high boreal poor fen 90 km south of Fort McMurray, Alberta. The importance of competitive interactions, habitat preference and regeneration capability to the existing community matrix was examined using transplant investigations and growth studies.; Sphagnum angustifolium has a very wide ecological amplitude. It is partially limited by habitat preference but competition and establishment do not locally limit this species. Dispersal is also probably not an inhibiting factor since Sphagnum angustifolium readily colonised many establishment tubs in which it was not planted. The very broad fundamental niche of Sphagnum magellanicum in this peatland is partially limited by habitat in that S. magellanicum cannot survive in the driest habitats. Further, Sphagnum magellanicum is likely not competitively excluded from any habitats but it is limited in its ability to colonise bare peat surfaces from asexual gametophytic fragments. Sphagnum fuscum is not limited by habitat as it can survive in all habitats, but the factors which prohibit this species full occupation of its fundamental niche are still not completely understood. The mature gametophytes of Sphagnum fuscum may be competitively excluded from the hollow habitats in this peatland by S. magellanicum. Establishment ability also likely plays an important role as Sphagnum fuscum appears to have a very narrow and specific regeneration niche which does not include postfire bare peat. The very narrow realised niche of Pleurozium schreberi in this peatland is the result of several restrictions. Pleurozium schreberi is competitively inferior to the Sphagna and therefore competitive exclusion is likely a factor. Pleurozium schreberi is also limited by habitat in that it can only survive in dry and shaded habitats, but it is quite capable of establishment on bare peat from gametophytic fragments.; Measurement of bryophyte growth was a method central to this thesis and many other examinations of bryophyte response to abiotic and biotic factors. Despite this importance, the weight that is actually gained or lost by the experimental shoots themselves is rarely measured, thus potentially leading to high experimental error. Therefore, an existing (but rarely used) method was modified, calibrated and field-tested in a back transplant experiment to allow for prediction of initial dry weight from moist weight of the experimental shoots.