REU: Plant-Herbivore Interactions in Stream Ecosystems

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Herbivory is a fundamental process in both aquatic and terrestrial ecosystems. Although herbivory is often viewed as simple plant consumption, numerous ecosystem features operate to determine the nature and outcome of plant-herbivore interactions. The basic premise of this research is that dynamics of the herbivory process in stream ecosystems are determined by the productive capacity of plant assemblages and the consumptive demand of herbivores. In many streams, benthic algae are the predominant plants, while macroinvertebrates such as insects and snails are the dominant herbivores. Because herbivores typically consume a large proportion (50%) of the plant biomass in streams, the potential for competition for limited resources is greater streams than in many other ecosystems. A combination of laboratory and field experiments will evaluate (1) the influence of ecosystem productive capacity on plant-herbivore interactions, (2) the intensity of competitive interactions among stream herbivores, and (3) the importance of the interaction between algal productivity and consumer dynamics to stream ecosystem structure and function. Results of these studies will be incorporated into the herbivory subsystem of a mathematical model of stream ecosystems. Implications of subsystem modifications will be assessed in terms of behavior of the total ecosystem model. Completion of the proposed research and modeling will allow crucial comparisons of herbivory to be made between aquatic and terrestrial ecosystems. Results of the research will enable stream ecologists to interpret herbivory relative to other important ecosystem processes, rather than as an isolated activity.//