Moira McCarthy

Human trade increases the spread of invasive species in urban areas, which can alter the composition of urban forests and outcompete native plant species. The disturbances caused by invasive earthworms in urban forests have been relatively understudied. Earthworms consume leaf litter that would otherwise be decomposed by microorganisms that return nutrients from the leaf litter into surface soils. The Twin Cities Metro Area is a unique study system because it is at the intersection of three ecological subsections: Anoka Sand Plains, St. Paul-Baldwin and Big Woods. I worked with the Minneapolis-St.Paul Urban Long Term Ecological Research Program (MSP-LTER) to study the effects of invasive earthworms on the ecological subsections in the metro area. I sought to answer the question: Is there a difference in earthworm species richness between the three ecological subsections and does sapling species richness change between ecological subsections? Sapling abundance and species richness were surveyed, as well as leaf litter bulk density. Earthworms were collected using mustard extraction and hand-sorting. There was a significant difference in sapling species richness between the three ecological subsections, but no significant relationship between earthworm species richness and the ecological subsections. Sapling species richness could be an indicator of earthworm invasion because species richness will likely change as the soil decreases in nutrients. To understand in greater depth how earthworms are impacting these ecological subsections, further analysis must be done to assess if there is a relationship between earthworm functional group presence and sapling abundance.