How build up soil bacterial co-occurrence networks from wide spatial scale sampling?
Résumé
Although land use drives soil bacterial diversity and community structure, little
information about the bacterial interaction networks is available. Here, we investigated
bacterial co-occurrence networks in soils under different types of land use (forests, grasslands,
crops and vineyards) by sampling 1798 sites in the French Soil Quality Monitoring Network
covering all of France. An increase in bacterial richness was observed from forests to
vineyards, whereas network complexity respectively decreased from 16,430 links to 2,046.
However, the ratio of positive to negative links within the bacterial networks ranged from 2.9 in
forests to 5.5 in vineyards. Networks structure was centered on the most connected genera
(called hub), which belonged to Bacteroidetes in forest and grassland soils, but to
Actinobacteria in vineyard soils. Overall, our study revealed that soil perturbation due to
intensive cropping reduces strongly the complexity of bacterial network although the richness is
increased. Moreover, the hub genera within the bacterial community shifted from copiotrophic
taxa in forest soils to more oligotrophic taxa in agricultural soils.