Responses of soil microathropods to invasion by exotic earthworms in hardwood-dominated stands of New York

Exotic earthworms native to Europe and Asia are rapidly altering biotic populations and communities in invaded habitats of North America. As earthworms change the physical and chemical properties of soil through intermixing of horizons, the impacts of earthworms are expected to be relatively high on native soil microarthropod species, especially those that have specific microhabitat requirements. We studied the effects of exotic earthworms on communities of soil microarthropods, specifically oribatid mites, in deciduous forests of central New York. During 2007-2009, all soil mites were extracted from two 1m2 plots in the following forest stands: 1) with no earthworms (control); 2) with epigaeic and endogaeic earthworms, but anecic earthworms such as Lumbricus terrestris, a deep soil-dwelling species, were absent; and 3) with all the three guilds of earthworms. Soil samples were collected in the spring and fall of each year, and all soil mites were extracted with Berlese funnels. At present 20 oribatid species have been identified and verified. Preliminary results suggest that forest stands with no earthworms had the greatest number of oribatid mites, with few mites present in stands with epigaeic and endogaeic earthworms, and almost none in the stands that have L. terrestris. As we continue our species identifications, we hope to provide a beeter understanding of the direct and indirect ecological cascading impacts of exotic earthworm on native biotic communities in northern hardwood forest stands.