Peanut-cotton intercropping to enhance soil ecosystem multifunctionality: Roles of microbial keystone taxa, assembly processes, and C-cycling profiles

Legume-based intercropping, such as the peanut-cotton system, stands out as a promising strategy for enhancing soil ecosystem multifunctionality (EMF); however, the underlying microbial mechanisms driving these enhancements remain inadequately explored. In this study, after implementing peanut-cotton intercropping for six consecutive years, a data set of 13 ecosystem functional indicators including 41 soil variables, was obtained and used to quantify the average EMF index. We investigated changes in microbial keystone taxa in co-occurrence networks, community assembly processes, carbon (C) cycling profiles, and their collective impacts on soil EMF. Soil EMF increased by an average of 140.0 % in the peanut-cotton intercropping system, compared with monoculture systems of both peanut and cotton, driven by significant increases in C-cycling (159.9 %), nutrient provisioning (91.2 %), and microbial growth efficiency functions (53.9 %). The peanut-cotton intercropping system significantly increased the average well-color developments (AWCD), abundance of C-fixation and Cdegradation genes, and related pathways, resulting in a highly vigorous microbial C-cycling profile. The microbial community assembly processes shifted from a balance of stochastic and deterministic processes in monocultures to predominantly deterministic processes (>70 %) in the intercropping system. Additionally, the peanut-cotton intercropping system fostered a more efficient and stable bacterial-fungal cross-kingdom network than the monocultures, characterized by a higher average clustering coefficient, higher robustness, and shorter average path length. This intercropping system also recruited a group of keystone taxa affiliated with Proteobacteria, Actinobacteria, and Ascomycota phyla. The enhancement of EMF in the peanut-cotton intercropping system resulted from the positive impact of key microbial community members and their assembly, C/N ratios, AWCD, and C-fixation and C-degradation genes. Our study provides insights into the complex ecological linkages between microbial communities, C-cycling profiles, and soil ecosystem functions, providing valuable insights into the microbial mechanisms underlying the benefits of intercropping systems.