Earthworm abundance and carbon cycling: relationships in northern glacial topography and earthworm species type

Abstract

Invasive European earthworm colonization in the Northern United States has a detrimental effect on forest ecology by decreasing overall species diversity. The earthworm behaviors that cause this ecosystem decline are viewed beneficially in an agricultural context, and lead to a discrepancy in the anthropogenic consideration of earthworm effects. We studied the impact of topographical and vegetative cover type properties according to glacial geography on the population size of invasive earthworms at the University of Michigan Biological Station by conducting field surveys of earthworm abundance. A Wilcoxon t-test showed significant differences between the mean population count of earthworms at moraine and outwash locations, while linear regression indicated that soil temperature at a depth of 5cm was the strongest predictor of earthworm abundance. We also studied the carbon cycling of two earthworm species, Lumbricus terrestris and Eiseniafetida, within controlled terrariums. The earthworm terrariums demonstrated significantly higher soil carbon content than the control, confirmed by a single sample t-test. These findings support our assumption that invasive European earthworms are highly efficient carbon recyclers, and that their environmental distribution is impacted by topographical characteristics.