Soil properties, habitat structure, climate, and topography as drivers of soil biodiversity

The Catalonia Plot System for Terrestrial Biodiversity Monitoring (SISEBIO) is a long-term project aiming to monitor above- and below-ground biodiversity changes due to global change in permanent experimental sites. The project aims: a) to catalogue the existing biodiversity using metabarcoding, b) to describe the environmental drivers explaining such, and c) to identify habitats acting as biodiversity hotspots.

For this purpose, 109 permanent plots were set up in natural areas to covering all the main habitats and climates of Catalonia (NE Spain). Plant, microbial (bacteria and fungi), protists, and microarthropods richness and diversity were assessed between 2018-2021, together with a variety of environmental drivers (soil physicochemical properties, habitat structure, climate, and topography). While plant diversity was assessed through traditional morphological identification, that of soil organisms was assessed by metabarcoding and using operational taxonomic units (OTUs) for this purpose.

Concerning soil biodiversity, 42077 unique OTUs were identified, with around 40% of them only found in once. The highest biodiversity values corresponded to sites located in the Pyrenees, and the environmental factors driving biodiversity were clearly different depending on the taxa studied. However, we failed to find habitat-specific hotspots except for microarthropods, with higher richness values in conifer forests when compared to deciduous forests, shrublands and grasslands.

The existence of biological interactions and historical factors may hinder the emergence of strong environmental trends to describe soil biodiversity patterns. Our results might may guide stakeholders with the implementation of management policies in the most vulnerable habitats to protect their biodiversity, but are also of interest for modelling the impact of global change on soil biodiversity and their ecosystem services.