Numerical and functional effects within a resource pulse driven community: Consequences for indirect interactions among prey.
Schmidt, Kenneth*,1, Ostfeld, Richard, 1 Texas Tech University, Lubbock, TX, 79409
ABSTRACT- Some of the clearest examples of the ramifying effects of resource pulses exist in deciduous and coniferous forests dominated by mast-producing trees, such as oaks, beech, hornbeam, and boreal conifers. Seed production in these forests represents only the first of several pulsed events. Secondary pulses emerge as mast-consuming small rodents numerically respond to seed production and tertiary pulses emerge as raptors numerically respond to rodents. In addition, raptors (e.g., Barred Owls) respond functionally to subsequent crashes in small rodents following the crash phase in seed production. In oak-dominated forest in the Hudson Valley of New York, these various pulse and crash phases act synergistically, although not simultaneously, to influence thrush population dynamics through predation on nests, juveniles, and adults. As a consequence, factors limiting population growth rate and their age-specific action vary as a function of past acorn production. We highlight these interactions based on our 8-yr study of thrush demography, acorn production, and small mammal abundance coupled with information on regional thrush population trends from the Breeding Bird Survey. We use these data sets to demonstrate the sequence of primary to tertiary pulses and how they influence breeding thrush populations. In addition we use population simulations to explore how the frequency, magnitude, and sequence of pulsed resource events can greatly influence long-term population trends among songbirds.
Key words: resource pulse, predator-prey interactions, numerical response, prey-switching
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