Exploring the biocrust microbial diversity in calanchi areas

In arid and semiarid environments, biological soil crusts (BSCs) are pivotal components of soil communities, demonstrating resilience even in extreme conditions such as “calanchi”, where severe erosion processes occur. Calanchi is an Italian plural term used to describe a unique type of badlands. These badlands are highly dissected landforms with steep slopes, loose sediments, and rare or absent vegetation. This study investigates the impact of soil degradation, driven by erosion processes, on the BSC microbial community within a Sicilian calanchi area. Ten sampling sites, each with distinct hillslope positions, vegetation covers, elevations, and degradation levels, were selected. From each site, two soil samples were collected and subjected to plate count, 16S rRNA, and amplicon sequencing analyses to determine microbial loads, species composition, and taxa identification across varying degradation levels: no degradation (ND), light degradation (LD), and severe degradation (SD). The findings indicate that the SD conditions are associated with significantly lower microbial loads compared to the ND and LD conditions, which exhibit comparable microbial loads. In terms of species composition, the onset of erosion in ND sites leads to an increase in both bacterial and fungal biodiversity, as measured by observed Operational Taxonomic Units (OTUs), due to the feedback effect of light degradation stress. However, as erosion intensifies and site degradation becomes severe, there is a marked reduction in observed OTUs, reflecting the inhospitable conditions for microorganism survival. Notably, the taxa detected in LD sites possess traits that enhance soil fertility and mitigate erosion processes. Conversely, severe degradation caused by soil erosion resulted in a microbial community predominantly composed of pathogens. The study highlights the potential of using fungal and bacterial taxa as bioindicators for monitoring ecosystem health and resilience