Résumé
Soil aggregate stability (i.e. the ability of soil aggregates to resist breakdown under disruptive forces) is crucial for the functioning of several ecosystem processes such as infiltration, carbon storage, nutrient cycling, resistance to erosion and ecosystem services related to these processes. In recent years, many studies have highlighted the importance of roots and soil microbial communities on soil aggregate formation and stabilization. Here we present the results of two complementary studies to understand linkages between soil biodiversity and soil aggregate stability: 1) a field study to understand how soil microbial diversity patterns are related to soil aggregate stability and 2) a mesocosm inoculation experiment to understand if soil microbial composition mediates the effects of roots and land use on soil aggregate stability. Study sites are natural forest, agroforest, arable and pasture fields in subalpine, temperate and Mediterranean regions in the UK and France. Aggregate stability was studied using the standard method ISO/CD 10930 and microbial diversity was assessed using Next Generation Sequencing. In the mesocosm inoculation experiment reciprocal inoculations of microbial communities crossed with root systems were compared to identify their influence on the aggregation properties. Results showed the existence of correlation between soil diversity patters and soil aggregate stability at different field sites. More interestingly, the mesocosm study showed that there is a direct effect of microbial inoculations on the stability of soil aggregates. This study provides valuable insights in the current emerging challenge of linking detected communities and their associated changes to relevant soil services, thereby providing new information to land managers on more sustainable forms of land management to optimise ecosystem services delivery, in this particular case, to services related to soil aggregate stability