Do diversity of plants, soil fungi and bacteria influence aggregate stability on ultramafic Ferralsols? A metagenomic approach in a tropical hotspot of biodiversity

International audience; Aims: Understanding how soil aggregate stability (MWD) is influenced by microbial diversity and abundance can be crucial for ecological restoration in severely disturbed areas. We investigated the relationships between plant and soil microbial diversity and MWD of an ultramafic Ferralsol along a vegetational succession gradient in New Caledonia, where wildfires and extensive nickel mining have degraded the landscape. Methods: Five plant communities were studied. For each one, MWD, soil physicochemical parameters (e.g. soil organic carbon (SOC)), plant root traits and fungal abundance were measured. The diversity and structure of plant and microbial communities were respectively assessed via botanical inventories and a metagenomic approach. A generalized linear model (GLM) was used to assess the influence of diversity indexes on MWD. Constrained ordinations (CCA) were performed to assess the influence of communities' structures on MWD. Results GLM highlighted the linkage between SOC and MWD but did not identify any significant influence of diversity indexes on MWD. CCA revealed a significant influence of communities' structures, especially the abundance of saprotrophic fungi, on MWD. Conclusions: We showed that the structure, but not species richness and diversity of plants, soil fungi and bacteria influence aggregate stability on Ferralsols.