The importance of topographic factors on the distribution of bog and heath in a Newfoundland blanket bog complex

It is commonly assumed that the development of blanket bogs is governed more by climatic factors than by topography, but no quantitative studies have been undertaken. The primary aim of this research was to quantitatively assess the extent and nature of the topographic influence of both the surface and the underlying substrate on the distribution of bog and heath communities within a blanket bog complex. Three blanket bog sites on the southeastern lobe of the Avalon Peninsula, Newfoundland, were studied. Terrain shape characteristics such as slope, plan and profile curvature, and upslope catchment area were derived from digital elevation models (DEMs) of surface and mineral substrate, and analysed using Partition d'un Ensemble Géographique pour l'Analyse Spatiale Ecologique (PEGASE), a procedure based on concepts from information theory. The analysis showed that topography accounted for approximately 22% of the structure underlying the distribution of bog and heath communities within the blanket bog complexes studied. Furthermore, only substrate morphology, which represents the topographic conditions at the initiation of peat accumulation, strongly affected the present pattern of bog and heath at the sites. Although lower elevations were more favourable for bog development, bog communities persisted in upper elevations in areas where the topography assisted in detaining water.