Using Tree Rings to Date the Arrival of Invasive European Earthworms

Investigators: Evan R. Larson, Kurt F. Kipfmueller, Cindy M. Hale, Lee E. Frelich, Peter B. Reich

We developed tree-ring chronologies from worm-invaded and worm-free areas within northern hardwood stands to identify a tree-ring signature associated with the invasion of European earthworms into previously worm-free areas. The identification of this signature will allow us to determine the timing of earthworm invasions throughout Minnesota, thereby providing a means to examine the long-term effects of this ecosystem engineer on native soils, nutrient cycles, and plant communities. In the process of identifying this signature, we also documented shifting climate-tree growth relationships in sugar maple trees following earthworm invasion with potentially important implications under future climate change scenarios.