Résumé
Soils are one of the major reservoirs of biological diversity on our planet, hosting a huge diversity of microorganisms. Numerous studies have demonstrated the role of microbial diversity in soil functions, such as nutrient cycling or pathogen management. Given the key role of soil microorganisms in the regulation of soil ecosystem functions, the environmental factors driving soil microbial diversity need to be understood. In France, we have the opportunity to benefit from a national soil survey (called the French Soil Quality Monitoring Network), which represents one of the most extensive and without a priori soil sampling survey available to date. Through several funded projects, we were able to decipher the spatial distribution of microbial diversity at the scale of France. These analyses provided extensive maps of microbial diversity, structure and composition and reveals the heterogeneous and spatially structured distribution of microbial communities at the nationwide scale. We also identified the ecological processes involved in the biogeographical patterns of microbial diversity, and develop co-occurring networks identified within the relative abundance of bacterial taxa dataset to the scale of France in order to better understand the processes involved in community assembly. From an operational point of view, innovative diagnosis tools were developed with obtained datasets, using statistical predictive models according to environmental parameters. They provide reference values fitted for a given pedoclimatic condition, which is to be compared to the corresponding measured data for a robust diagnosis of soil biological quality. These innovative tools allow a robust diagnosis of soil biological quality.