Effects of Herbivory, Competition, and Disturbance on a Wetland Plant Community with Emphasis on the Dominant Aquatic Macrophyte, Nymphaea Odorata Aiton
To examine the contribution of seed banks to the formation of distinct plant assemblages after a physical disturbance, plant percent cover on and off floating islands was assessed in the field. A controlled greenhouse seed bank experiment in which water levels were manipulated was also conducted. Emergent plants dominated floating islands, which were characterized by localized declines in inundation, whereas N. odorata dominated undisturbed sites. Assemblages in the greenhouse experiment differed among water level treatments in a manner consistent with differences observed in the field. This suggests that floating island formation temporarily altered inundation favoring the germination of a more species-rich, emergent plant assemblage, and may be one mechanism maintaining otherwise rare plant populations. These experiments suggest that herbivory and disturbance are more important than competition for regulating N. odorata and for influencing the surrounding deep-water marsh community at this site.