Above- and below-ground effects of an exotic ecosystem engineer in the boreal forest

• Author / Creator

  Cameron, Erin K

• Species invasions are increasing worldwide and are impacting populations, communities, and ecosystems. Non-native species that are ecosystem engineers, such as earthworms, may be particularly likely to have large impacts due to their ability to modify both biological and physical characteristics of their environment. Using a combination of field and laboratory studies, I examined above- and below-ground effects of non-native earthworms in the boreal forest of Alberta. I found no evidence that earthworm species facilitate each other’s invasions or have synergistic effects, as would be expected in an invasional meltdown. In a mesocosm experiment, the litter-dwelling earthworm Dendrobaena octaedra and the deep-burrowing species Lumbricus terrestris did not facilitate each other’s survival or reproduction. Similarly, although the two earthworm species significantly influenced microarthropod abundance, oribatid assemblage structure, and leaf litter depths, they did not have synergistic effects. Further, white spruce (Picea glauca) growth and colonization of white spruce roots by mycorrhizal fungi were not affected. Earthworms impacted other taxa via both direct trophic interactions and ecosystem engineering. In laboratory experiments, changes in soil structure associated with earthworm burrowing had strong effects on both microarthropod movement and plant root growth. In contrast, a field study indicated that distributions of American robins and earthworms were strongly correlated, suggesting the two groups are linked via predation of earthworms by robins. Although this research indicates non-native earthworms are affecting a variety of taxa in the boreal forest, there is limited awareness of earthworm invasions among the public. Consequently, a combination of increased research, public education, and regulations will likely be needed to effectively manage earthworm invasions in Alberta.

• Subjects / Keywords

  • Earthworms
  • Facilitation
  • Ecosystem engineer
  • Invasions
  • Boreal

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3RX00

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.