Soil biological quality across land-use gradients: An arthropod-based index from a comprehensive literature review

Biological indicators are increasingly used to assess soil health, yet global reference values remain scarce for most metrics. The QBS-ar index (Soil Biological Quality based on arthropods), which evaluates the degree of adaptation of soil microarthropods to edaphic conditions, is now widely applied, but comparative benchmarks across ecosystems and regions have been lacking. This study presents a global meta-analysis of QBS-ar, synthesizing 826 observations published between 2002 and 2025 across 16 countries and seven major land-use categories. Data were extracted and standardized by land use, management system, and disturbance type, and analysed using non-parametric methods. QBS-ar values ranged from 0 to 417 (mean: 110). Forests, vineyards and orchards, and grasslands showed the highest values, whereas agricultural and urban areas consistently exhibited lower scores. Organic agriculture performed significantly better than conventional and no-tillage systems, underscoring the positive effects of reduced chemical inputs and enhanced organic matter. Severe disturbances—including contamination, mining, and historical military activity—were associated with the lowest values. Spatial patterns indicated substantial geographic variability linked to land-use intensity and site history. To facilitate interpretation, we developed QBS-ar explorer, an interactive tool that positions user-provided values within the global distribution of published data. By providing the most comprehensive dataset and analysis of QBS-ar to date, this study establishes an essential international reference framework for interpreting soil biological quality. The results highlight both the sensitivity of QBS-ar to ecological gradients and anthropogenic pressures and the need for methodological standardization—particularly in EMI classification—to enable robust global comparisons and to support the development of reliable benchmarks for soil health assessment.