Ecological Mechanisms and Scaling in Heterogeneous Grassland Ecosystems

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The proposed research will (a) develop theory linking the responses of individuals to spatial variation in population and ecosystem dynamics; (b) test such theory by experimental field studies and simulation modeling; (c) determine how ecological features vary with spatial scale and whether "rules" can be defined for extrapolating among scales; and (d) extend this work to systems composed of tropically linked species. The field research, conducted in a semiarid grassland ecosystem, will involve experimental studies of responses of tenebrionid beetles to the spatial structure of "microlandscapes" and to variations in spatial patterns at broader scales. Individual movement patterns at fine scales will be coupled with long-distance movements to determine how individual behavior translates into population distribution. Experiments with harvester ants will be used to determine how the removal and transport of seeds are affected by the spatial structure of ecosystems. Scaling relationships among linked trophic levels will be investigated using horned lizard-ant and longspur-grasshopper systems. The research bears directly on current issues in ecological scaling and extrapolation, flows of materials across patch boundaries, empirical testing of spatial models, and the development of an experimental and theoretical approach to landscape ecology.