Earthworm_decaying_root_3An underground invasion of European earthworms in glaciated forests in North America has compounding impacts on the capacity of the soil to provide nutrients and sequester carbon.

Kyungsoo Yoo, University of Delaware, and colleagues Anthony Aufdenkampe of the Stroud Water Research Center and Cindy Hale, an ecologist at the University of Minnesota Duluth, were recently awarded a three-year, $397,500 grant from the U.S. Department of Agriculture National Research Initiative (USDA-NRI) to study the quantitative coupling of the ecology of European earthworm invasion – specifically in Canada, New England and the Great Lakes region – with mineral chemical weathering and carbon cycling.

According to Yoo, 10 to 20 years ago, hikers in Minnesota’s forests noticed that the leaf litter layer was rapidly disappearing. Hale’s doctoral research (see references) showed that non-native earthworms were slowly eating their way into the forest, mixing the litter layer into the mineral soils in the process.
“Soil scientists and agriculturalists recognize the benefits of mixing organic matter with the mineral soil in production agriculture,” Yoo says. “However, in native forests the leaf litter is essential to the survival of native trees’ seedlings. The litter layer provides protection for temperature changes and deer browse. As earthworms invade and consume the leaves, the layer and therefore the success of seedlings, is compromised.”
He adds, “This relationship has been singled out as one of the most important factors impacting the future sustainability of forests in the glaciated areas in the U.S.”

It is estimated that the invading front of earthworms migrates as much as 7 meters each year further into a forest. As these waves of earthworms move into an area, they change the structure and the bio-geochemistry, accelerating the mineral/chemical weathering, which has an impact on carbon-mineral interactions.
“We are looking at the integration of biology, chemistry, and physics in a mechanical fashion. We would like to know and understand how and how fast the sustainability of forests is affected by the invasion of these nonnative species,” Yoo says.


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