Browsing by Subject "Lumbricus rubellus"

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    Earthworm invasion into previously earthworm-free temperate and boreal forests
    (2006) Frelich, Lee E; Hale, Cindy M; Scheu, Stefan; Holdsworth, Andrew R; Heneghan, Liam; Bohlen, Patrick J; Reich, Peter B
    Earthworms are keystone detritivores that can influence primary producers by changing seedbed conditions, soil characteristics, flow of water, nutrients and carbon, and plant–herbivore interactions. The invasion of European earthworms into previously earthworm-free temperate and boreal forests of North America dominated by Acer, Quercus, Betula, Pinus and Populus has provided ample opportunity to observe how earthworms engineer ecosystems. Impacts vary with soil parent material, land use history, and assemblage of invading earthworm species. Earthworms reduce the thickness of organic layers, increase the bulk density of soils and incorporate litter and humus materials into deeper horizons of the soil profile, thereby affecting the whole soil food web and the above ground plant community. Mixing of organic and mineral materials turns mor into mull humus which significantly changes the distribution and community composition of the soil microflora and seedbed conditions for vascular plants. In some forests earthworm invasion leads to reduced availability and increased leaching of N and P in soil horizons where most fine roots are concentrated. Earthworms can contribute to a forest decline syndrome, and forest herbs in the genera Aralia, Botrychium, Osmorhiza, Trillium, Uvularia, and Viola are reduced in abundance during earthworm invasion. The degree of plant recovery after invasion varies greatly among sites and depends on complex interactions with soil processes and herbivores. These changes are likely to alter competitive relationships among plant species, possibly facilitating invasion of exotic plant species such as Rhamnus cathartica into North American forests, leading to as yet unknown changes in successional trajectory.
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    A study of herbaceous vegetation in Chequamegon - Nicolet National Forest: relationship of earthworms, white-tailed deer browsing and Carex pensylvanica Lam
    (2014-12) Ojanen, Paul Thomas
    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.