PARENT SESSION
Symposium 23: Body Size, Biophysics and Biological Stoichiometry: From Individual Function to Ecosystem Structure
Organized by: J Sabo and B Enquist
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Chatham Ballroom B.
Thermal context dependency: The influence of climate and energetics on spatially explicit patterns of food web structure and dynamics.
Sabo, John*,1, Porter, Warren2, Reichman, Jim3, 1 Arizona State University, Tempe, AZ2 University of Wisconsin-Madison, Madison, WI3 National Center for Ecological Analysis and Synthesis, Santa Barbara, CA
ABSTRACT- One of the greatest challenges to a general theory of food web dynamics is understanding how food web structure varies with ecological contexts. Contexts are diverse and include biotic factors such as the abundance or recruitment of a particular species, as well as abiotic factors like flooding, wave action or climate. Many of the classic experiments on intertidal communities as well as more recent studies of food webs in both aquatic and terrestrial habitats suggest that context dependency is prevalent and a potentially useful framework for understanding and characterizing variability in food web dynamics at meaningful spatial and temporal scales. One important context in terrestrial landscapes is the thermal environment. Local climate is patchy at a variety of spatial scales across the landscape. The goal of this talk is to explore how variability in the thermal environment may determine spatial variation in food web structure (presence/absence of herbivores and carnivores) and food web dynamics (i.e. interaction strength between predators and prey) in terrestrial ecosystems. To do this, we first apply newly developed biophysical models to predict spatially explicit patterns of individual activity and energetics for a suite of hypothetical predator-prey pairs varying in body size and mode of temperature regulation (ecto- and endotherms). We then use predicted values of metabolic rates, "discretionary energy" (the energy available for growth and reproduction), and activity time from biophysical models as parameters in models of population growth for these predator and prey species. In this way we provide a framework for linking landscape variables (slope and aspect) directly to per capita rates of energy consumption and encounter. These per capita rates in turn determine the relative growth rates and standing stocks of predator and prey populations. We then illustrate how our model predictions could be used as testable hypotheses in field experiments designed to evaluate how the strength of predator prey interactions and the prevalence of trophic cascades vary across real landscapes.
Key words: biophysics, food web, body size, temperature