PRF: Factors Controlling Periphyton Abundance and ProductionDuring Stream Sucession

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A central question in ecology has been whether abundance and production at a given trophic level are limited by resources or by higher trophic levels (predation, grazing). This project includes research to answer that question for primary producers (periphyton) of a desert stream ecosystem during its recovery or succession following flash flooding. A first project is to provide background information on grazer population dynamics and energetics which heretofore have not been studied in this system. Project 2 will utilize field manipulations of both resource availability (nitrogen concentration) and grazer abundance to determine how limiting factors change over successional time. This will add to an increasing base of knowledge of how stream ecosystems respond to and recover from disturbance (flash flooding). The third project will explore effects of grazing intensity on primary production using grazer density manipulations. If grazing is found to stimulate primary production, hypotheses explaining the mechanism of stimulation will be tested experimentally. If grazing is not stimulatory, an attempt will be made to explain why nutrients released by grazers are not recycled to stream periphyton. This final project deals with a controversial topic in ecology, the question of whether herbivory may actually prove beneficial to plants that are eaten. Dr. Nancy B. Grimm's approach differs from others in that experimental field manipulations will be used to test hypotheses. Arizona State University will serve as the host institution during the two-year postdoctoral fellowship tenure.