Ants Under Climate Change at Harvard Forest and Duke Forest 2009-2015

Experimental field studies are needed to understand the consequences of global
climatic change for local community structure and associated ecosystem processes. We
are using 5-m diameter open-top environmental chambers and 1m pvc minichambers to
simultaneously manipulate air and soil temperatures at the Harvard Forest and at the
Duke Forest in North Carolina. These field manipulations are designed to 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: 1. 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. 2. Warming will change the relative
abundance and composition of ant communities, and will lead to the loss of ant
biodiversity. 3. Warming will potentially diminish ecosystem processes and services
provided by ants, particularly with respect to the dispersal of seeds. To explore
these, we are conducting two experiments. In one experiment, twelve open-top chambers
at each site which will each be exposed air temperatures ranging from 1.5 to 7 deg C
above ambient; soil temperatures will be increased simultaneously from 0 to ~ 2 deg
C. After an initial year of pre-intervention measurements, the experiment will run
for 3 consecutive years of continuous warming. In the second experiment, shade cloth
and plastic greenhouse sheeting will be used to increase or decrease temperature by
0.5 deg C in sixty minichambers. The minichamber experiment was conducted in 2009 and
will continue into 2010. The response variables measured in both experiments 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.