Influence of earthworm abundance and diversity on soil structure and the implications for soil services throughout the season

Earthworms help maintain and enhance the physical condition and function of soils. Their contribution to soil services, such as the flow of water, nutrients and gases, is influenced by earthworm abundance and diversity. In this study mesocosms with either low (dominated by epigeic Lumbricus rubellus) or high earthworm abundance and diversity (L. rubellus, Aporrectodea caliginosa and Aporrectodea Tonga) were established to explore the relationship with plant production, soil porosity and soil moisture over 444 days. Mesocosms with an abundant and diverse earthworm community had 5% more micro-pores and 70% more macropores. Volumetric soil moisture contents were consistently lower in the mesocosms with an abundant and diverse earthworm community and above-ground accumulation of plant biomass was 35-70% higher over the last 5 months of the study. There was a strong positive relationship between earthworm abundance and diversity, drainage and plant growth and negative relationship with soil moisture. The influence of earthworms on pasture growth was greatest during winter and spring, while their effect on drainage volume was more pronounced during the drier period. This work provides baseline information demonstrating how to relate earthworm abundance and diversity to soil services, and highlights the need to consider their changing influence throughout the season.