Cindy Hale
Friday, October 17, 2008 - 11:00-11:30
Non-native earthworms have invaded previously earthworm-free forests in the northern U.S. These forests historically had thick forest floor layers that served as rooting medium for herbs and trees and provided habitat for vertebrates and invertebrates. Following invasion, by non-native earthworms, a cascade of ecological effects can occur including the loss of the thick forest floor, large declines in native plants and tree regeneration, compaction and increased erosion in surface soil horizons, and nutrient leaching. These structural and functional changes in a forest result in loss of habitat plus the collapse of a diverse arthopod community. This, in turn, can contribute to large declines in salamanders and ground-nesting birds. Compositional changes may also occur in populations of small mammals. The magnitude and types of impact by nonnative earthworms on forested ecosystems are related to biomass and species of earthworms present. In general, large and diverse populations of earthworms are supported in forests with mesic soil conditions and palatable hardwood litter. Humans are the primary source of earthworm introductions and their distributions are associated with duration and intensity of human activity. Earthworm-free or minimally impacted forests still remain throughout the Great Lakes region of the northern US and Canada. Action taken now could limit the spread of nonnative earthworms, prevent the introduction of additional species and help to prevent the spread of earthworms in the Asian genus Amynthas that are still uncommon in most of North America yet known to cause severe impacts outside of their native ranges.
Keywords: EXOTIC SPECIES, EARTHWORMS, ECOSYSTEM CHANGE, HARDWOOD FOREST