Earthworms and soil biogeochemical processes

Earthworms inhabit almost all ecosystems and they play an important role in the soil's functioning. Through their burrowing activities, i.e., the ingestion and egestion of mineral soil and organic material, they actively change their surrounding environment, consequently altering the hydrological and biogeochemical properties of the soil. In addition to the physical burrowing, the physical and chemical properties of earthworm casts differ from the surrounding soil material, thus affecting the water retention properties, as well as the soil's density. However, differences exist between earthworm species in to which regard and degree their bioturbation influences the soil structure. More specifically, different species can have opposite effects, highlighting the impact of the loss of species, e.g., through soil and land management. Overall, when assessing the presence of earthworms, it is recommended to consider the soil as a system in order to include the interactions between individual parts. Mathematical models are powerful tools in this regard, as earthworm processes, such as bioturbation, are highly dynamic and influence on different parts of the soil system.