Evan Larson '02 shares his expertise with an environmental science class

by University Communications,

For a fisher, earthworms are bait.

For a forest, they mean complete alteration of the forest floor environment, a loss of biodiversity and increased drought susceptibility.

“When we talk about the creatures that inhabit the world, some creatures have a disproportionate impact,” says Evan Larson ’02, an assistant professor of geography at the University of Wisconsin-Platteville. “These ecosystem engineers literally engineer the environment in which they live.”

As a specialist in dendrochronology, Larson analyzed tree rings to determine when the earthworms arrived at sites in northern Minnesota and Wisconsin.

On Feb. 26, Larson shared his research with the Willamette community in a lecture titled, “Invasive Earthworms as Ecosystem Engineers: Using Tree Rings to Track Earthworm Impacts on Forests in the Great Lakes Region of North America.”

During his visit to Willamette, Larson also interacted with an environmental science class, both in the lab and at Zena forest.

Stevie Gildehaus ’13 valued the opportunity to learn from Larson, who helped her with the research for her environmental science thesis.

“He’s been helping me with analysis, to determine what’s affecting our tree rings at Zena forest,” Gildehaus says. “Picking up the signals in the tree rings is really difficult, and it is fascinating to see how connected everything is.”

In addition to his innovative work tracking earthworm invasions, Larson runs a tree ring lab at the University of Wisconsin-Platteville — using tree rings to reconstruct past disturbances to forests, such as fire, climate change and human activity.

Larson says he got hooked on dendrochronology as an undergraduate in Willamette's Science Collaborative Research Program (SCRP), under the mentorship of environmental science professor Karen Arabas.

“My SCRP experience is absolutely why I am where I am right now,” Larson says. “The project that I was involved with laid the foundation for my career, it gave me the skills that I now use daily in my own research program and it connected me to the importance of research experience as an undergraduate student.

“Willamette is a wonderful place, so I’m glad I could come back and contribute to the culture that makes it great.”

Larson’s visit was sponsored by the Department of Environmental and Earth Sciences and an Atkinson research grant.