A Critical Re-Examination of Food Web Patterns in Real Ecosystems

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The central aim of this proposed research is to provide a critical reappraisal of so-called empirical laws of trophic structure in real ecosystems. In collaboration with researchers at the University of Wisconsin Trout Lake Station, and the Wisconsin Department of Natural Resources, the first whole-system data base designed specifically to represent the trophic structure of a large-scale ecosystem will be assembled. Because aquatic environments represent the largest fraction of systems upon which the food web laws are based, this effort will focus on Little Rock Lake, a long-term study site which has been extensively studied as part of an ongoing experimental acid rain monitoring project, and which promises to yield a suite of 24 highly detailed food web data sets. A pilot study confirmed the availability of a surprisingly large amount of trophic information here and the relatively high degree of taxonomic and temporal resolution that could be attempted. Amount the details that will be included in this study are: a full and more even- handed resolution of the species involved and their feeding intensities; temporal variability in food web structure with season and ontogeny; the effects on food web patterns of studying incomplete subsystems; and the variation in food web structure introduced by systematically changing the resolution of the data through aggregation and the incorporation of major to minor interactions. The following are some of the questions being asked. How representative of real systems ar ethe data upon which many food web generalizations are based? How dependent are food web properties on the temporal and taxonomic resolution of the data? When is a property such as food chain length truly limited by the environment or simply by the quality of the data?