Patrick Lavelle

5 - Earthworms as Key Actors in Self-Organized Soil Systems

This chapter describes the drilosphere, which is defined as an earthworm population, all the biogenic structures that they build in the soil, and the communities of smaller organisms that inhabit these structures. The chapter shows that drilospheres have all the characteristics of self-organizing systems. It also discusses the theoretical and practical meaning of this organization. The chapter presents the interactions with micro-organisms and other inhabitants of the drilosphere that allow earthworms to derive energy from decomposing organic matter. The chapter describes the physical domains created in soils by the accumulation and spatial array of biogenic structures (earthworm casts, galleries, voids, and middens), addressing the effects of this system on the soil environment and the possible positive feedbacks provided in return to earthworms and inhabitants of the drilosphere. It also discusses how effective management of the drilospheres relates to sustained provision of soil ecosystem services, such as water infiltration and storage, C-sequestration, and nutrient cycling.