Second
growth northern
hardwoods near
Leech Lake, Minnesota. Photo
by Dave Hansen,
University of
Minnesota Agricultural
Experiment Station. 
Base
of sugar maple,
no earthworms. Photo
by Dave Hansen,
University of
Minnesota Agricultural
Experiment Station. 
Base
of sugar maple,
with earthworms. Photo
by Dave Hansen,
University of
Minnesota Agricultural
Experiment Station. 
Nodding
Trillium above
and Bellwort
below, two species
negatively impacted
by European earthworms. Photo
by Dave Hansen,
University of
Minnesota Agricultural
Experiment Station.
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