Conservation of species diversity requires understanding the processes that maintain diversity over time. The objectives of this research were to assess the relationship between environmental conditions and vascular plant diversity in lakeside fens, elucidate the history and ecological effects of the cattail Typha × glauca in coastal fens, and evaluate the relative roles and importance of Lake Ontario coastal versus inland fens for supporting plant diversity.
I measured diversity and composition of vascular plants in 4 Lake Ontario fens and 4 inland fens in relation to hydrology, forest canopy cover, water chemistry, and microtopography. Inland fens were found to be the most species-rich and forested areas were more species-rich than open areas. Dominance of Typha × glauca and Osmunda regalis in flooding-stressed and light-stressed habitats respectively suggests a refinement of centrifugal organization theory.
Using a microcosm fertilization and competition experiment, I examined the growth, biomass allocation, and competitive effect of Typha × glauca and its parent species at 3 nutrient levels. No evidence was found for heterosis in T. × glauca, however greater height of T. × glauca relative to parent species and reduced herbivory upon it may contribute to its competitive dominance in the field.
I examined plant macrofossil stratigraphy from 3 coastal and 3 inland wetlands. Inland systems developed via lake-fill succession and showed a tendency toward rapid succession to bog-like vegetation with reversals to minerotrophy. Coastal wetlands developed when uplands were flooded by rising Lake Ontario waters in the late Holocene. Coastal wetlands showed less variability in habitat than the inland sites over the last ∼2000 years.
Using pollen and macrofossil analysis I investigated the long-term dynamics of vegetation in a Lake Ontario wetland. Pre-European sedge-dominated vegetation gave way to Typha by the mid 20th century. Monad and diad pollen grains in pre-European strata suggest that putatively exotic T. angustifolia and T. × glauca may have been present prior to European settlement.
The differences in current diversity and long-term development between inland and coastal wetlands indicate that efforts to protect both types of wetland may protect the greatest diversity over time.
Key Words: diversity, centrifugal organization, nutrients, Typha, cattail, hybridization, invasive plants, paleoecology, macrofossil, pollen, Lake Ontario, fen, peatland, wetland, succession
