U.S. Department of Energy, Office of Science

Program for Ecosystem Research

Research Project   Impacts of elevated temperature on ant species, communities, and ecological roles in two temperate forests in eastern North America

Principal investigator:   Robert R. Dunn

Project goal

Determine effects of warming on the populations, communities, and associated ecosystem services of assemblages of ground-foraging ants. Specific hypotheses to be tested are that warming projected by climate models for the coming 100 years in the eastern United States will (1) lead to declines in ant species' abundances at the warmer, southern extent of their present ranges; (2) change the relative abundance and composition of ant communities, leading to loss of ant biodiversity; and (3) potentially diminish ecosystem processes and services provided by ants, particularly with respect to the dispersal of seeds of understory herbs.

Ecosystem being studied

Picture of Aphaenogaster tennesseensis

An individual Aphaenogaster tennesseensis in North Carolina. This ant species is expected to become more rare with warming, a notion that will be directly tested with the project's field experiment. [Benoit Guenard]

The field experiments will be conducted in the understory of temperate hardwood forests in Massachusetts and North Carolina. The study organisms will be a range of ant species living at the sites.

Results

The infrastructure needed to conduct the field warming experiments is being constructed at the research sites.

Why this is important

This project will determine effects of warming on populations and communities of ants at the northern (cool) and southern (warm) ends of their present ranges in the eastern United States. Ants are a model taxon for studying effects of climatic change on animals because they comprise the largest fraction of animal biomass in many terrestrial ecosystems, and because ants provide several essential ecosystem services such as soil turnover and plant seed dispersal.

This set of field experiments uses a regression-based experimental design rather than the more common "plus-or-minus" warming treatments. Because of this, the study may be more likely than most to identify which temperatures (and therefore which greenhouse gas concentrations) might be "safe" for terrestrial ecosystems and the organisms that they contain. The study is also well suited to determining whether potential nonlinear and/or threshold effects of warming on ant communities (and by extension other animal groups and associated ecosystem processes) might occur in a warmer world.

This study will provide a unique experimental test of the hypothesis that animal species at the northern (cool) and southern (warm) boundaries of their ranges will respond predictably to climatic change. In addition, the research will provide a basis for establishing ants as a model animal taxon for the experimental study of potential ecological effects of climatic change.

Methods

Ten open-top chambers will be installed in the forest understory at each site (i.e., in Masschusetts and in North Carolina). Each chamber will be controlled to one of ten levels of temperature, ranging from the present ambient temperature at each site to 5 degrees Celsius above the present ambient conditions. The 5 degree Celsius warming is consistent with projections for the year 2100 as summarized by the most recent Intergovernmental Panel on Climate Change (IPCC) synthesis report.

After an initial year of pre-treatment measurements, the experiment is designed to run for three consecutive years with continuous warming. The measured response variables will include: ant activity, population densities and colony sizes of focal ant species, ant community diversity and species composition, and rates of tree seed dispersal and predation as mediated by ants.

Personnel

Robert R. Dunn, North Carolina State University

Aaron Ellison, Harvard Forest (subaward)

Nicholas Gotelli, University of Vermont (subaward)

Nathan J. Sanders, University of Tennessee (subaward)

Funding period:   January 2008 to present