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Kim C. Diver, Dana L. Royer, Helen M Poulos


Earth and Environmental Sciences




The fundamental principle of island biogeography is to explain species richness in insular habitats. MacArthur and Wilson (1967) theorized that island area and island isolation are the two main drivers of plant species richness. In the study area, The Massasauga Provincial Park in Lake Huron, it has been proposed that there are alternative variables affecting plant species richness (Diver, 2004). The aim of this study is to explore community structure within The Massasauga with statistical approaches not traditionally used in island biogeography. I examined the influence of traditional island biogeography variables (e.g. area and isolation) as well as soil pH, habitat heterogeneity, community structure, and forest dynamics on plant and tree species richness in The Massasauga.

Plant species-area and plant species-isolation relationships in The Massasauga were significant (81.24% and 58.19% respectively). Ordination revealed that the strongest significant factor affecting tree species richness was isolation, measured as the amount of land within a 500 m buffer (R2= 0.554). Island size did not have a significant effect on tree species richness. There was no relationship between soil pH and plant or tree species diversity (R2=0.001 P=0.7617). A strong negative relationship existed between the minimum soil pH value per island and the density of white cedar trees on the island (R2=0.621 P=0.0014). Cluster analysis revealed three main vegetation types: red maple, red oak, and white cedar. The red maple vegetation type was more common on inner islands, and the white cedar vegetation type was more common on outer islands. Size-class diagrams of tree species present in The Massasauga indicate a trend shifting from a pine forest to a pine-oak forest. The overstories of the islands are expected to become more diverse in the next generation.

Studying island biogeography within the context of community ecology reveals new insights into plant species richness in The Massasauga. Applying diverse statistical techniques revealed new information regarding the spatial variability of plant species richness and reaffirmed traditional theories of island biogeography.

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