Land-use affects soil microbial co-occurrence networks and their putative functions

Soil microbial interactions are crucial in performing ecosystem functions. The microbial co-occurrence network could shed a new understanding of microbial functioning as affected by land management. Current studies on microbial community interactions mainly considered surface soils, thus the understanding of the microbial interactions and functions in the subsoils is still limited. We investigated soil samples from undisturbed remnant forests and disturbed vineyards in top-(0-25 cm) and subsoils (40-100 cm) in the Hunter Valley region, New South Wales, Australia. Soil microbial communities of bacteria and fungi were characterized by analyses of 16S rRNA and ITS amplicon sequencing, respectively. Land use differences caused the variances of soil properties, as resulted in the differences of microbial community composition and diversity, especially for the topsoils. Moreover, we found that agriculture activities had influenced the microbial networks for both the top-and subsoils. Widely connected bacterial networks were found in forest soils but they appeared as highly centralized clusters in vineyards for both layers. Although the interactions within those network clusters were enhanced in cropping soils, the connections between the clusters decreased or even isolated. We also characterized bacterial functions for element cycling based on their putative functions. Agricultural disturbances decreased the variability of C cycling bacteria for both surface and below layers, and reduced bacteria abundances working for C cycling in the topsoils. Additionally, soil bacterial co-occurrence network clusters were found to be correlated with microbial functions for element cycling, which demonstrated the significant influences of microbial network structure for microbial biological functions.