Ant Diversity and Vegetation Composition in Hemlock Removal Experiment at Harvard Forest 2006

Ants comprise a considerable amount of animal biomass in terrestrial ecosystems and play major roles in ecological processes ranging from seed dispersal to soil turnover. Invasion by the hemlock woolly adelgid will transform late-successional hemlock forests into earlier successional mixed hardwood-white pine forests or red-maple wetlands. Understanding how ant assemblages vary in different habitat types allows for predictions of how hemlock decline could alter the composition of ant assemblages, with implications for a wide range of ecosystem processes. An ongoing study at the Simes Tract of Harvard Forest is documenting the effects of invasion and land-use history on ant biodiversity. Surveys from 2003 to 2005 focused on ant structure in hemlock and hardwood microhabitats in the Harvard Forest Hemlock Removal Experiment, in which hemlock forest response to deforestation by the hemlock woolly adelgid (Adelges tsugae) and to selective logging is being examined (Ellison et al. 2005). In the summer of 2006, we surveyed a greater range of microhabitat types with two objectives. First, to collect rare or elusive species in hemlock and hardwood stands that may have gone uncollected in previous years. Second, to sample forest communities not included in previous years - white pine, swamp, and rocky slope - for ant species unique to these microhabitats. We found fourteen newly documented species of ants in the Simes Tract - nine of which were in an open, swamp. Aphaenogaster rudis and Camponotus pennsylvanicus were the only ant species found in all microhabitat types. In a canonical correspondence analysis, A. rudis and C. pennsylvanicus were associated most strongly with hemlock stands and low species richness of understory plants.