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Harvard Forest Symposium Abstract 2013

• Title: Interspecific interactions in changing environments: how do community context and abiotic conditions shape the outcome of plant-granivore interactions?
• Primary Author: Rafa Zwolak (Adam Mickiewicz University)
• Additional Authors: Elizabeth Crone (Tufts University)
• Abstract:

  Certain interspecific interactions cannot be easily classified: they involve both costs and benefits, and the balance of these determines where the net outcome falls between mutualism and antagonism. Plant-granivore interactions are particularly well-suited for investigations of such context-dependent interactions. Many vertebrate granivores consume some seeds, but cache others in favorable microsites, and their ultimate impact on plant recruitment may vary with environmental conditions. We will experimentally test the influence of biotic (masting and community context) and abiotic (weather conditions affecting seedling recruitment) factors on the outcome of interactions between oaks and rodent acorn consumers in two complementary study systems.
  
  
  
  At Harvard Forest, we will evaluate the extent to which masting and environmental conditions qualitatively shift oak (Quercus spp.) – mouse (Peromyscus) interactions from antagonistic, in which mice act as seed consumers and have a negative effect on oak regeneration, to mutualistic, in which mice act as seed dispersers, with a positive effect on oak regeneration. Specifically, we are testing the effects of changes in animal communities and acorn production on mouse behavior, and demography, and on acorn germination and seedling establishment. We will test effects of masting by comparing the area with chronic-N addition (which increases acorn production ~ threefold (Callahan et al. 2008 Global Change Biology 14:285-293) to alternative parts of Harvard Forest with similar forest communities, that have not been subjected to N supplementation. We will test effects of changes in mammal communities by working in the ungulate exclosure plots at the hemlock removal experiments; oak seedlings are present in these plots. Both studies involve a combination of small mammal trapping, acorn tracking, and seed germination studies in and outside of small mammal exclusion cages.
  
  

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