Responses of soil microarthropods to soil metal fractions under different mediterranean vegetation covers

Abstract

Soil microarthropods play essential roles in soil functioning and they are considered useful indicators of soil metal contamination, as they quickly respond to environmental changes. The toxicity of metals depends on their fractions, but few studies have been conducted on the responses of microarthropods to different metal fractions. The study aimed to assess the response of the soil microarthropods to the soil metal fractions (exchangeable: available for organisms, reducible: associated to Fe-Mn oxides, oxidizable: associated to organic matter) under different Mediterranean vegetation covers. To reach the aim, the soils of different vegetation covers (holm oak, pine, black locust and herbs) were analysed for pH, water content, total C, N and P and Corg, NH4+ and Passimilable contents, the exchangeable (F1), reducible (F2) and oxidizable (F3) fractions of Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn and the microarthropod taxonomic and functional indices. The results showed that, regardless the vegetation cover, the F2 and F3 of Ca, Cr, Cu, Fe, K, Mg, Mn, V and Zn significantly inhibited the density of microarthropods, favouring the functional traits typical of disturbed environments. The element F1, except for Mn, slightly impacted on the microarthropod community. In addition, the soils under trees positively influenced the taxonomic and functional indices of the microarthropod community where higher contents of Corg and macronutrients were observed. Several taxa were differently impacted by three metal fractions of Al, Ca, Fe and K; in particular, Formicidae were favoured, whereas Diplopoda and Isopoda were favoured by Ca, Fe and K and inhibited by Al concentrations. The present research demonstrated that stable fractions (F2 and F3) of metals, instead to available one, exert a strong impact of microarthropod community. This leaded to change in microarthropod community assemblage, favouring taxa and traits typical of disturbed environments.