PARENT SESSION
Oral Session 6: Herbivory I: Dynamics, Communities, and Photosynthesis.
Presiding: C Ivey
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 114.
The effects of herbivory on growth, production, and resource allocation in Nymphaea odorata.
Cherry, Julia *,1, Gough, Laura2, 1 University of Alabama, Tuscaloosa, Alabama2 University of Texas at Arlington, Arlington, Texas
ABSTRACT- The extent to which herbivores influence the composition and function of plant communities is not well understood, but herbivory is potentially an important factor structuring ecosystems by influencing biodiversity, productivity, and energy flows within food webs. Generalizations concerning the effects of herbivores on aquatic macrophytes, and the consequent effect on ecosystem-level processes are lacking. During a two-year exclosure study in the field, we controlled semi-aquatic insect herbivory of the dominant macrophyte, Nymphaea odorata, to ascertain if the plant compensates for the loss of biomass due to grazing. In general, leaf density, biomass, turnover rates and annual aboveground net primary production were greater in plots in which plants were grazed, suggesting that compensatory growth does occur in N. odorata. Based on research suggesting that herbivory can cause reallocation of biomass and nutrients within plants, we also established a simulated two-year herbivory experiment in the greenhouse to investigate resource and biomass allocation in plants experiencing different levels of grazing intensity. Results indicate that plants experiencing no and moderate damage (i.e., 5% of leaf surface area removed) had greater aboveground and belowground biomass than plants experiencing high levels of damage (i.e., 15% of leaf surface area removed), suggesting that there is a threshold of grazing intensity under which plants are capable of compensatory growth. The majority of leaf damage in the field was within the range of 0 – 6% of leaf surface area corresponding to the no and moderate levels in the greenhouse experiment. Therefore, compensation in the field was likely possible because the threshold of grazing intensity was not exceeded.
Key words: aquatic macrophytes, resource allocation, herbivory, compensation