One of the biggest challenges for advancing our understanding of the role of soil organisms in regulating ecosystem functioning is to link changes in the diversity and structure of soil biological communities to biogeochemical processes at an ecosystem scale. A major hurdle in meeting this challenge is making sense of the enormous taxonomic diversity of belowground communities and its functional importance in soil. But new approaches, based on functional diversity of soil communities rather than on their taxonomic diversity, offer a way forward. For instance, it is now possible to quantify the diversity of functional genes and metagenomes, and the expression of functional genes, and relate these measures to ecosystem functions at meaningful scales. Moreover, trait-based approaches, which focus on the functional characteristics of organisms rather than their taxonomic identity, are increasingly being used to explain how shifts in the structure of complex animal and microbial communities impact the functioning of soil. The goal of this session is to explore how such new approaches in soil ecology can offer new insights into the functional significance of changes in biodiversity of soil, and how this knowledge can be used to better predict the consequences of belowground biodiversity for ecosystem functioning.