The dark side of biodiversity: Spatial application of the biological soil quality indicator (BSQ)

We conducted a comprehensive assessment of soil quality in South Tyrol, Italy by combining spatial land use and land cover data with field surveys studying soil microarthropods. The biological soil-quality index (BSQ) proposed by Parisi et al. (2005) is based on the assumption that higher soil quality is associated with the occurrence of more microarthropod groups that are well-adapted to soil habitats. We used the BSQ concept in the context of a state-wide sustainability assessment on a municipality level. Many soil animals fulfil key ecosystem functions that are the basis for significant and broadly used ecosystem services. These functions and services are essential for any sustainable agriculture type. To determine if and how BSQ values are influenced by land use characteristics, we analysed field data from 243 sampling sites comprising eleven different land cover or land use types. An ordinary least square regression (OLS) was used to assess the influence of land use types, altitude, aspect, slope and geology as independent variables on BSQ values (R2 = 0.60; p < 0.001). In addition to high variability in soil microarthropod communities, there were significant differences in BSQ values among most land use types. BSQ values were highest in forest ecosystems and lowest in arable fields. The parameters of the linear regression model were used together with spatial comprehensive GIS data to predict BSQ values spatially. The predicted values ranged from 0 to 198 and were used to calculate area-weighted mean BSQ values for all municipalities in South Tyrol. Our results show that the BSQ reacts sensitively to land use and hence can serve as an important surrogate indicator for sustainable land use practices.