| Floodplain wetlands are characterized by seasonal flood disturbance. River flooding increases water level fluctuations, brings dissolved nutrients, and removes plant litter. A railroad embankment in 1915 altered the natural connections to the Athabasca River by bisecting the floodplain in Jasper National Park. Diversity, community structure, productivity and nutrient availability were investigated in floodplain marshes with varied river connectivity. Unique vegetation community types were observed in the disconnected, partially river-connected and fully river-connected marshes. Lack of flooding resulted in peat development, increased moss growth, and wetland succession to a fen. Moderately flooded marshes had the highest diversity (45 species), supporting the Intermediate Disturbance Hypothesis, and highest productivity. A high flood year resulted in decreased productivity in all floodplain wetlands and increased nutrient concentrations in river-connected marshes. Large flood disturbance, rather than low nutrients, may be more important in determining vegetation communities, diversity, productivity, and ecosystem stability in the fully river-connected marshes. |
