Soil biota contributions to soil aggregation

Humankind depends on the sustainability of soils for its survival and well-being. Threatened by a rapidly changing world, our soils suffer from degradation and biodiversity loss, making it increasingly important to understand the role of soil biodiversity in soil aggregation—a key parameter for soil sustainability. Here, we provide evidence of the contribution of soil biota to soil aggregation on macro- and microaggregate scales, and evaluate how specific traits, soil biota groups and species interactions contribute to this. We conducted a global meta-analysis comprising 279 soil biota species. Our study shows a clear positive effect of soil biota on soil aggregation, with bacteria and fungi generally appearing to be more important for soil aggregation than soil animals. Bacteria contribute strongly to both macro- and microaggregates while fungi strongly affect macroaggregation. Motility, body size and population density were important traits modulating effect sizes. Investigating species interactions across major taxonomic groups revealed their beneficial impact on soil aggregation. At the broadest level, our results highlight the need to consider biodiversity as a causal factor in soil aggregation. This will require a shift from the current management and physicochemical perspective to an approach that fully embraces the significance of soil organisms, their diversity and interactions. The structuring of soil into distinct aggregates is a key element in biogeochemical cycling. Here, a meta-analysis reveals a strong positive effect of soil biota on soil aggregation, with the largest influence coming from bacteria and fungi.