Invasive earthworms alter multiple forest components. By accelerating litter decomposition, they alter nutrient flows, soil composition and vegetative communities. White -tailed Deer (Odocoileus virginianus) are known to alter vegetative communities by selective browsing; severity varies with population density and affects plant community population and composition. Both factors are associated with reduced vegetative community richness and dominance by graminoids. In this study, 101 randomly selected Northern Mesic Hardwood Sugar Maple sites in the Chequamegon - Nicolet National Forest were sampled for vegetation, earthworm occurrence and browsing intensity. Over three years, eighty-two percent of sites were positive for earthworms; in two non-drought years, ninety percent of sites were positive. Non-metric Multi-dimensional Scaling (NMDS) and Multiple Response Permutation Procedure (MRPP) found divergent communities; a Carex pensylvanica Lam dominated community associated with earthworm invasion and strongly linked to Lumbricus rubellus presence, and remaining Acer saccharum seedling stands associated with reduced earthworm impacts. Additionally Carex pensylvanica was strongly linked to Lumbricus rubellus presence by Indicator Species Analysis. Lumbricus rubellus invaded sites had both reduced species richness and vegetative cover. White-tailed deer (Odocoileus virginianus) browsing was found to be heavy and extensive throughout both forests, impacting Acer saccharum regeneration and further driving graminoid dominance. The results indicate earthworm invasion is geographically extensive and a principal driver of Carex pensylvanica understory dominance and reduced Acer saccharum regeneration.
University of Minnesota M.S. thesis. December 2014. Major: Natural Resources Science and Management. Advisor: Lee E. Frelich. 1 computer file (PDF); viii, 81 pages, appendices A-F.
Ojanen, Paul Thomas.
A study of herbaceous vegetation in Chequamegon - Nicolet National Forest: relationship of earthworms, white-tailed deer browsing and Carex pensylvanica Lam.
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