Soil Biological Quality index (QBS-ar): 15 years of application at global scale

During the last century, soils have been over-exploited by humans through agriculture and industrial development. The need to assess different aspects of soil degradation has become a priority in the soil protection management. Among several indices developed in the last years, QBS-ar (Soil Biological Quality-arthropod) index joins the biodiversity of soil microarthropods community with the degree of soil vulnerability. Up to now, numerous publications have reported the results of the QBS-ar application. This paper starts a review process for QBS-ar assessment by taking into account its potential in highlighting the relationship between soil quality and different land uses. In order to clarify the relationship between QBS-ar values and land use, we collected 41 published papers that reported of QBS-ar applications. In this framework, another aim of this paper is to make a critical review of the QBS-ar in respect to applications in different environmental contexts, and to obtain critical indication about problem and potential of QBS-ar for monitoring activities. We collected published data on QBS-ar and we individualized eight groupages in relation to soil uses: 1) Agriculture lands (A, several crops, till and no-tillage, organic, conventional), 2) Woods (W, forests, maquis and bushes), 3) Restored (R, plant remediation, restored pit mine, peri-urban uncultivated areas), 4) Natural degradation (ND, soils in natural degraded conditions, e.g. serpentine soils, soil in the brÛlé), 5) Permanent grasslands, pastures and meadows (G), 6) Orchards (O), 7) Urban parks, residual urban woods, public gardens, botanical gardens, home gardens (UP), 8) Soils involved in human degradation (D). The results confirmed that land use significantly affects QBS-ar values. The overall mean of QBS-ar = 93.7 can be considered a tentative threshold that separates high quality soils and values which are typical for poor soils. In the end, we would like to affirm the validity of this index, which, allows to evaluate the suffering state of soils and its potentiality for an expeditious use to evaluate soil biological quality in recovery areas.