Soil fauna are key components of soil biodiversity and contribute to decomposition, nutrient cycling, soil structure formation and the regulation of biological processes in agricultural soils. However, soil faunal responses to management are often assessed using different metrics, such as activity density, density, biomass and taxonomic richness, which may reflect distinct biological processes. As a result, it remains unclear whether agricultural practices that benefit one dimension of soil fauna also support others.

We conducted a meta-analysis of peer-reviewed field studies from European agricultural landscapes to compare how cropping intensity, crop type, farming type and agri-environmental measures affect soil fauna communities relative to intensively managed arable references. The dataset included 1,383 paired observations from 43 publications and covered major soil fauna groups and management contexts. Effect sizes were calculated as log response ratios and analysed using multilevel random-effects models that accounted for between-study heterogeneity and dependencies among comparisons sharing controls. We further evaluated whether responses differed among soil fauna metrics and major decomposer taxa.

Soil fauna responses varied strongly among metrics. Lower cropping intensity and agri-environmental measures produced the clearest positive effects on density and biomass, suggesting that reduced disturbance, permanent or semi-natural vegetation, and more continuous resource inputs favour the build-up of larger and more abundant soil fauna communities. Farming type was more closely associated with activity density and taxonomic richness, with organic or ecological farming generally showing positive effects. Crop type alone showed weaker and less consistent responses. Among individual agri-environmental measures, forests, fallows, grasslands, habitat strips and field margins generally supported higher density or biomass, whereas richness responses were more variable. Taxon-specific analyses showed that positive responses were concentrated in several decomposer groups, including Acari, Collembola, Enchytraeidae, Lumbricidae and Nematoda, although the strength of evidence differed among taxa.

Our results show that soil fauna metrics are not interchangeable indicators of biological soil condition. Density and biomass responded most consistently to management interventions, whereas activity density and richness were more context-dependent. Integrating multiple soil fauna metrics and taxon-specific responses can therefore improve biological assessment of agricultural soils and support the design of management practices that better conserve soil biodiversity