Plant species richness and its determinants on a coastal dune system at Îles de la Madeleine, Québec (Canada)

On coastal dunes, significant changes in several environmental factors that affect plant species richness, such as salt spray, substrate salinity, and sand movement, occur as distance inland from the beach increases. In the present study, I test a model (confirmatory path analysis) of the environmental factors controlling plant species richness on the ridges and in the slacks of a coastal dune system at Iles de la Madeleine, Quebec, Canada. Elevation, substrate organic matter, pH and salinity, and plant species richness were determined in 50-m2 quadrats on 9 ridges and 9 slacks along each of 12 transects perpendicular to the coastline. Each variable was analyzed for differences between ridges and slacks and among distances from the high drift line. Path analysis allowed me to determine the effects of the abiotic variables on species richness, separately for ridges and for slacks. Elevation, substrate organic matter, pH and salinity, and richness all varied substantially with distance from the hig...