Earthworms (Annelida: Oligochaeta) of the Columbia River Basin Assessment Area

James, Sam. 2000. Earthworms (Annelida: Oligochaeta) of the Columbia River basin assessment area. Gen. Tech. Rep. PNW-GTR-491. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 13 p. Earthworms are key components of many terrestrial ecosystems; however, little is known of their ecology, distribution, and taxonomy in the eastern interior Columbia River basin assessment area (hereafter referred to as the basin assessment area). This report summarizes the main issues about the ecology of earthworms and their impact on the physical and chemical status of the soil. The three main ecological types of earthworms found in the basin assessment area are epigeic, endogeic, and anecic. Each type has a different life history pattern, resource requirement, and ecological function. Effects of environmental and habitat variables in the basin assessment area on these three types are summarized. Key ecological functions of earthworms are presented in relation to the ecological types and habitats of earthworms in the basin assessment area. These key ecological functions include the effects of earthworms on soils, their role in nutrient cycling, and their relation to other fauna. Distributions of earthworm species in the basin assessment area also are summarized. Although most of the known species from the area are exotics from Europe, at least three species are native to the region. Unpublished records indicate that there may be many more species that have either not yet been collected or for which descriptions have not yet been published. Both the possibility of discovering additional macrofaunal biodiversity and the precarious status of at least one known species argue for additional research on earthworms in the basin assessment area. Effects of land use and management practices on earthworms are explored by examining research on similar human influences in other ecosystems as no research on these issues has been done in the Western United States. Suggestions for land use and future research priorities are provided.