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Revision as of 09:50, 21 May 2009
- Rob Dunn, North Carolina State University
- Aaron Ellison, Harvard University, Harvard Forest
- Nick Gotelli, University of Vermont
- Nate Sanders, University of Tennessee
Experimental field studies are needed to understand the consequences of global climatic change for local community structure and associated ecosystem processes. We propose to use large open-top environmental chambers to simultaneously manipulate air and soil temperatures using a statistically powerful and cost-efficient response-surface (regression) design at two field sites situated in northern and southern temperate mixed hardwood forests in eastern North America (Harvard Forest in Massachusetts, Duke Forest in North Carolina). The proposed field manipulations will reveal the effects of temperature increases on the populations, communities, and associated ecosystem services of assemblages of ground-foraging ants. Ants are a model taxon for studying effects of global climatic change because they comprise the dominant fraction of animal biomass in many terrestrial communities and because they provide essential ecosystem services, including soil turnover, decomposition, and seed dispersal. The experiment is designed to test three predictions:
- Projected atmospheric warming will lead to declines in ant species abundances at the warmer, southern extent of their ranges in the US. Conversely, projected atmospheric warming will lead to increases in abundance or range extensions of ant species at the cooler, northern extent of their ranges in the US.
- Warming will change the relative abundance and composition of ant communities, and will lead to the loss of ant biodiversity.
- Warming will potentially diminish ecosystem processes and services provided by ants, particularly with respect to the dispersal of seeds.
Twelve open-top chambers at each site which will each be exposed to one of four levels of air temperature increases, ranging from no change (ambient conditions) to 8 degrees C (commensurate with some IPCC climate model forecasts for the year 2100). The experiment will run for 3 consecutive years of continuous warming. The response variables measured will include ant activity, population densities and colony sizes of focal species, ant community diversity and species composition, and rates of seed dispersal and predation as mediated by ants. This study will provide an experimental test of the hypothesis that species at the northern and southern boundaries of their ranges will respond predictably to climatic change. In addition, this research will further establish ants as a model taxon for the study of climatic change.