Soil microbial communities in the face of changing farming practices: a case study in a 1,200 ha landscape in France

According to biogeography studies, the abundance and diversity of soil microorganisms vary across multiple spatial scales according to soil properties and farming practices. However, soil microorganisms also exhibit poorly understood temporal variations. This study aimed at better understanding how soil microbial communities respond to changes in farming practices at a landscape scale over time. A regular grid of 269 sites was set up across a 1,200 ha farming landscape, and soil samples were characterized for their molecular microbial biomass and bacterial diversity at two dates (2011 and 2016). A mapping approach highlighted that spatial microbial patterns were stable over time, while abundance and diversity levels were modified. The drivers of these changes were investigated though a PLS-PM approach. Soil properties were stable over time, but farming practices changed. Molecular microbial biomass was mainly driven by soil resources, whereas bacterial diversity depended on both farming practices and ecological parameters. Previous-crop and management effects and a temporal dependence of the microbial community on the historical farming management were also highlighted.