Exotic earthworm distributions did not expand over a decade in a hardwood forest in New York state

The ranges of exotic earthworms have been expanding into previously earthworm-free areas in temperate forests of North America. These earthworms can have profound effects on soil properties and biogeochemical processes, but the rate and patterns of earthworm range expansion has received limited study. We assessed long-term (2001-2011) changes in earthworm distributions along two belt transects (60-75. m long) in a northern hardwood forest in central New York. We expected long-term increases in earthworm abundance at the presumed earthworm invasion front. We also quantified earthworm populations in seven monospecific plantations of different tree species. We expected higher earthworm abundance in hardwood than conifer forests. We observed large annual fluctuations in earthworm abundance along both transects but no evidence of increasing abundance or range expansion at the earthworm fronts. At the plantation site we observed significant variation in earthworm abundance both within and among plantations, but the patterns were not consistently related to tree species composition; rather, earthworm abundance was highest in areas of higher soil pH and topographically wetter soils. Further study of environmental and biotic factors controlling the range expansion of exotic earthworms is needed at both local and regional scale.