Earthworm activity can alter forests' carbon-carrying ca...(s clay it might be a long-term way of st...)

Another way earthworm activity may affect the fate of carbon and the environment is in the thickness of layers of leaves and debris left on forest floors. Bare soil is generally very dark, absorbing more sunlight, which may dry it out quickly. A layer of lightly colored leaves is moderately reflective and holds moisture near the soil. Either condition may affect factors such as the warming of forest soil and the timing of snowmelt.

"Ultimately, we will look at such things to determine the potential invasive earthworms have in changing the flux of CO₂ out of the forest and how much that could impact climate change," said Filley, who also is an associate professor of earth and atmospheric sciences.

The earthworms that the team studies were brought to North America by early European colonists, probably in the ships' ballasts or in plant soil. In northern North American forests the settlers found land devoid of such creatures because the worms never reoccupied soils formed when the glaciers melted.

In addition, earthworms don't move very fast. It's estimated they have migrated under their own power only about 100-200 kilometers in the past 10,000 years since the glaciers.

"In some forests, such as ones we are working at in northern Minnesota, we find soils where earthworms are only now being introduced." Filley said. "The main agents of introduction in such areas are discarded fishing bait in nearby lakes, transport between forest sites in tire treads and the movement of soil."

The research team reported findings of their ongoing study in a recent issue of the Journal of Geophysical Research. The National Science Foundation has provided funds to continue the work.

For this study, Filley, Johnston and their collaborators monitor earthworm activity at the Smithsonian Environmental Research Center forest area in Maryland. The scientis
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