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Long-Term Data on Ants Reveal Forest Dynamics

April 9, 2018
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Sydne Record with Summer Student Collecting Ants

When forests change, do the ants that live there change, too? Ecologist Sydne Record (Bryn Mawr College), Aaron Ellison (HF Senior Ecologist), Tempest McCabe (Harvard Forest Summer Student '15, now at Boston University), and Ben Baiser (University of Florida-Gainesville) answered this question in a new study in Ecosphere

Ants provide many services to forests: they aerate soils, decompose wood, and disperse seeds. However, these services depend on the community diversity of the ants, which is linked to the composition of the trees. The new study investigated whether the death of trees from a certain species shifted the number of ant species living in the forest, or the number of services the ant community provides.

They collected ants at two sites: one site with oaks removed (Black Rock Forest's Future of Oak Forests Experiment), and one site with hemlocks removed (the Harvard Forest Hemlock Removal Experiment). Then for twelve years, they watched how ant community diversity changed compared to the same oak and eastern hemlock forests without the tree removals.

They found that the way the ant community changed depended on the type of forest. When eastern hemlocks were lost, the ant community changed, as did some of the services the ant community could provide. When oaks were lost, the ant community did not change in terms of species composition or the services that they provide.

This work implies that different trees have different levels of influence over their surrounding ecosystem. This research suggests that eastern hemlock defines its ecosystem - a hallmark of what scientists call a "foundation species" - and that removing those trees has effects that cascade all the way down to the ants. Removing an oak, on the other hand, has fewer effects.

As tree-specific invasive pests like the hemlock woolly adelgid continue to invade our region, understanding how the loss of particular tree species will affect an ecosystem is essential for conservation and management efforts.

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