The Arthropod-based Biological Soil Quality index (QBS-ar): three-year application in the Sentina reserve (Italy)

Soil microarthropods are reliable soil health indicators, as they are highly sensitive to alterations in soil conditions and mechanical disturbances. However, taxonomic identification for most of the taxa is rarely performed as it requires the involvement of expert taxonomists and the use of molecular techniques. In contrast, soil microarthropod morphological traits are commonly used as indicators, as exemplified by the arthropod-based soil biological quality index (QBS-ar). The aim of the study was to apply the QBS-ar index to monitor the soil health of farms located within the Sentina Reserve (Italy), over a three-year period (2021-2023) across two seasons (spring and autumn). The objective was to assess the ability of the index to discriminate between different levels of intensity of agricultural practices applied in two conventionally managed farms (FE= high intensity, RL= low intensity). To determine the impact of the agronomic practices (i.e., tillage depth, fertilizers and pesticides application, use of nitrogen-fixing and cover crops) on soil microarthropods, two sites (i.e., arable fields) were selected for each farm. The QBS-ar, and other indices, including density were determined. The soil microarthropod community composition was analysed using ordination analysis. Over the three-year, high biological soil quality was observed in all sites and seasons. The highest QBS-ar scores were recorded in 2023, probably due to a rainy season. Generally, RL farm showed a better performance compared to FE; QBS-ar and microarthropod density were significantly higher in RL than FE in spring (124 vs 103| 2138 vs 870 ind/1000cm3) and autumn (132 vs 105|3626 vs 1046 ind/1000cm3). Interestingly, microarthropod community composition differed between farms, although not significantly. The farms were located within a protected area, characterised by a mosaic of arable land, grasslands, dunes and wetlands. This high landscape complexity has possibly contributed to the maintenance of an excellent soil quality, serving as a reservoir for biodiversity. This was crucial for the recolonization of the arable land by soil fauna, following soil disturbance. Moreover, less intense and sustainable soil management, proved their effectiveness in the preservation of edaphic biodiversity and soil health. The QBS-ar index confirmed its reliability in the detection of different levels of disturbance in arable lands.