Ciliated Protist Communities in Soil: Contrasting Patterns in Natural Sites and Arable Lands across Italy

This study represents the first investigation of soil ciliate diversity and community structure in the Marche region, Italy, encompassing both natural sites and agro-ecosystems. The main aims were (i) to assess the ability of ciliates to discriminate between different types of land uses, i.e., arable lands and possible farming management practices [organic (ORG) vs. conventional (CON)], and forest (FOR) sites; and (ii) to investigate the relationships among ciliate communities and abiotic parameters at the studied sites. Soil samples were collected twice from 10 sites (5 forest (FOR) (natural soils) and 5 arable lands under different agricultural management systems (3 ORG (minimum tillage) and 2 CON (sod seeding)). Ciliate communities were studied using qualitative (non-flooded Petri dish) and quantitative methods (ciliate counts from permanent slides). Soil chemical-physical (texture, CEC, N, OM, C/N) parameters were also measured. Qualitative ciliate analysis allowed us to identify a total of 59 species representing 33 genera, 20 families, 13 orders, and 7 classes. ORG sites were the richest in species followed by CON and FOR. Multivariate analysis showed statistically significant differences between natural sites (FOR) and agricultural sites, and between ORG and CON management farming systems. CCA analysis revealed a positive correlation between the ciliate species and silt, clay, and pH in ORG sites, and sand, organic carbon, organic matter, total nitrogen, C/N ratio, and CEC (cation exchange capacity) in FOR sites, suggesting the significance of these parameters in shaping the ciliate communities. Altogether, these results showed the bioindicative potential of ciliate communities in discriminating between natural sites (FOR) and arable lands, and their capacity to discriminate, at least preliminarily, between different soil management systems (ORG vs. CON). Furthermore, this study highlights the high diversity of soil ciliates and their response to habitat variability