Patterns of Distribution

Exotic earthworms invading forests that were naturally devoid of large detritivores can cause major changes in ecosystem function. To assess their long-term impacts, studies are needed to clarify the factors that control the patterns of earthworm invasion at the landscape level. A study published in Landscape Ecology showed the distribution patterns of exotic earthworms in a northern hardwood forest in south-central New York as explained by landscape variables thought to be important in determining earthworm distribution. Forest type, slope angle, elevation and the distance to agricultural clearings and wet refugia were significant predictors of earthworm presence, whereas local wetness index and the distance to streams and roads were not. Forest type and distance to agricultural clearings were the two most significant predictors. Areas close to agricultural clearings, dominated by mixed hardwoods and located towards valley bottoms or on gentle slopes are very likely to support communities of exotic earthworms. Steeper slopes, areas dominated by American beech or eastern hemlock and locations in the core of extensive forest landscapes have lower probabilities of invasion by exotic earthworms. (Suarez et al 2006)