Vegetation and habitat conditions in Western Head Bog, a southern Nova Scotian plateau bog

Publisher Website
Google Scholar
Abstract
The southernmost plateau bogs in eastern North America are found in southern Nova Scotia. They are characterized by an extremely wet plateau with high conical hummocks, a partly forested bog slope, and several disjunct species of the Coastal Plain flora.Prevailing water levels on the plateau are high and fluctuate little. They do not start to drop until very close to the plateau margin, and are lowest on the forested parts of the slope. The lagg is wet and has the most strongly fluctuating water levels.Water table location, and thus microtopography of the surface, controls the vegetation pattern of the plateau. A Gaylussacia baccata dwarf shrub heath occupies hummocks 25 cm or more above the 50% summer water table. Utricularia mud bottoms are regularly flooded in summer and the water table never drops more than 5 cm below the surface. The two Scirpus lawn communities occupy an intermediate position.A complex gradient, involving both water level and nutrient regime, controls vegetation changes from the center to the bog border. The bog slope, especially under the forest, is enriched by the detritus cycle. Floristic changes in the vegetation indicate an enrichment of the plateau margin, and possibly also the slope, by drainage water seeping from the plateau. Peat analyses failed to confirm this. Within the lagg, differences in minerotrophy separate the two fen communities, but floristic changes on the hummocks are caused by differences in water table location, nutrient supply, and shading.These plateau bogs are distinguished clearly from those along the west side of the Bay of Fundy by the dominance of mud bottoms rather than lawn communities on the plateau, by the occurrence of many nutrient-demanding species in the ombrotrophic vegetation, and by the presence of Coastal Plain disjuncts, such as Ilex glabra.