ABSTRACT

Spatial scaling of microorganisms has been demonstrated over the last decade. However, the processes and environmental filters shaping soil microbial community on a wide scale still need to be identified and their hierarchy established. Here, we performed the first comparison of bacterial and fungal diversity turnovers through Taxa-Area Relationship on the same widescale soil sampling. Molecular fingerprinting of soil bacterial and fungal communities was performed on 413 soils from four French regions of contrasting environmental heterogeneity (Landes<Burgundy≤Brittany<<South-East, area range: 13800 to 33500 km2) using the systematic grid of French Soil Quality Monitoring Network to evaluate the communities’ turnovers. The relative importance of processes and filters was assessed by distance-based redundancy analysis. This study demonstrates significant turnover rates for soil bacterial and fungal diversity, which were dependent on the region and organism. Bacterial and fungal diversity turnovers were driven by similar processes, with environmental selection explaining from 10% to 20 % of community assembly variations whereas dispersal limitation explained only from 3% to 9%. Although the filters and their hierarchy were also dependent on the region and organism, selection was mainly based on pH, trophic resources, texture and land use, and dispersal was limited at coarse (80 to 120km radius) and/or medium (40 to 65km radius) spatial scales. In a context of sustainable soil management, the preservation of soil biological patrimony by the maintenance of diverse and spatially structured habitat must be fitted to regional heterogeneity and ecological attributes of soil microorganisms.