The surprising link between deer, invasive earthworms and tree harvesting

by Lori Fligge, University of Minnesota
April 18, 2023

There’s a surprising and highly influential link between invasive earthworms, white-tailed deer and tree harvesting in northern forests, according to new research from the University of Minnesota.

The findings, recently published open access in the journal Ecology, show invasive earthworm populations increase with deer presence and decrease with tree harvesting. Increased earthworm invasion is cause for concern because the species is known to harm soil and regenerating trees.

“”Invasive earthworms are ecosystem engineers which negatively impact fundamental ecosystem properties such as nutrient retention and the diversity of native plant species. Deer exacerbate these negative impacts by increasing earthworm populations,” said Lee Frelich, an adjunct professor in the Department of Forest Resources and Director of the Center for Forest Ecology.

The team of U of M researchers, in collaboration with the U.S. Forest Service, the Wisconsin Department of Natural Resources and others, sampled earthworms in two long-term experiments in northern Wisconsin. Both experiment sites were established in the mid-2000s and simulated deer exclosures and tree harvesting — which leaves behind a large canopy gap in the overstory.

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