Microarthropods of the soil, convergence phenomena and evaluation ofsoil quality using QBS

The increasing recognition of problems deriving from soil degradation has contributed in identifying soil fauna research as a priority in soil quality assessment. In par-ticular, soil microarthropods have been shown to respond sensitively to land management practices and to be corre-lated with beneficial soil functions. The growing interest in the employment of living organisms for the evaluation of soil conditions is justified by the great potentiality of these techniques, which allow the measurement of factors diffi-cult to notice with physical-chemical methods while giving information that is easier to understand. The basic idea of bio-indications is that the relationship between soil factors and soil communities can be preserved. In this article, two indices based on edaphic microarthropods have been pro-posed to assess biological soil quality. The first, the QBS-ar index, is based on the entire microarthropod community present in a soil sample. Each �morphological type� found in the soil sample receives a score from 1 to 20 (Eco-Mor-phological Index, EMI), according to its adaptation to soil environment. The QBS-ar index sums these scores, thereby characterizing the microarthropod community of the sam-ple being studied. QBS-ar has been applied on a range of soil types and land uses in Italy, and its validity evaluated for assessing the biological quality of soil in different situa-tions. The second index, called QBS-C, is based only on the Collembolan community and considers all EMI values of biological forms in the extracted soil sample. QBS-C index, in spite of its application being more difficult, proves highly effective in the evaluation of differences in soils character-ized by different organic matter content, moisture and mechanical tillage