Great Lakes Worm Watch

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Worm Research Studies around the Nation

Effects on Plants

Assessing the impacts of European earthworm invasions in beech-maple hardwood and aspen-fir boreal forests of the western Great Lakes region

Total earthworm biomass supported by beech-maple forests was nearly half that reported in sugar maple dominated forests and the total earthworm biomass supported by aspen-fir forests was half that of the beech-maple forests. Comparisons to earthworm-free stands were not possible and are needed to further explore any potential causal relationships between earthworm and understory plant populations.

Location: Voyageurs National Park, MN & Pictured Rocks National Lakeshore, MI
Lead Researchers:
Cindy Hale, Ph.D. & George Host, Ph.D., University of Minnesota Duluth - Natural Resources Research Institute
full text

Exotic earthworm abundance in west central Minnesota

This study surveyed for earthworms using the liquid extraction method in five forested study areas in west central Minnesota—the town of Morris, the University of Minnesota, Morris campus and three State Parks.  Contrary to a published study suggesting a link between earthworms and invasive European buckthorn (Rhamnus cathartica), the project revealed an inverse correlation between earthworm abundance and buckthorn abundance in the study plots at the State Park sites.

Location: West Central Minnesota
Lead Researchers:
Andy Shaffer and Peter Wyckoff, University of Minnesota Morris
full poster presentation

Greenhouse microcosm

The primary objective of this study was to identify the factors affecting the recovery of understory plants and tree seedlings following an invasion of earthworm populations. This information is invaluable for the development of strategies to protect and restore hardwood forest ecosystems as earthworms continue to expand their range.

Location: Duluth, MN
Lead Researcher:
Cindy Hale, Ph.D., University of Minnesota Duluth - Natural Resources Research Institute

Influence of Exotic Earthworms on the Soil Organic Horizon and the Rare Fern Botrychium mormo

To determine whether there is an association between the presence of an exotic earthworm species and extirpation of the rare goblin fern Botrychium mormo, this study surveyed 28 populations documented and counted previously.   This study estimated current population sizes of B. mormo, soil horizon thickness, earthworm species present, and carbon content, nitrogen content, and pH of the A soil horizon. Lumbricus rubellus was significantly associated with B. mormo extirpation and a mull humus type.  The results of this project support the idea that exotic earthworms alter the forest floor, leading to negative changes in native vegetation.

Location: Chippewa & Chequamegon & Nicollette National Forests
Lead Researcher: Michael Gundale, University of Montana - School of Forestry
Full Abstract

Effects of leaf litter depth on the emergence and seedling growth of deciduous forest tree species in relation to seed size

Leaf litter has a major impact on soil microenvironmental conditions and so can
be an important influence on seedling recruitment and hence plant community structure. This study conducted a greenhouse experiment to examine the impact of leaf litter from temperate deciduous forests on the emergence and growth of tree seedlings in relation to seed size.

Location: New York
Lead Researchers: Kostel-Hughes et al, Fordham University
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