Soil microbial composition, diversity, and network stability in intercropping versus monoculture responded differently to drought

Drought alters the diversity, composition, and network stability of microbial communities. Natural resources benefit from intercropping, particularly cereal-legume intercropping, where soil microbes are important for biogeochemical cycles and plant growth. However, little is understood about how different cropping environments' soil microbial communities respond to drought. Here, we examined bulk and rhizospheric soil microbial communities in the cereal/legume monoculture versus intercropping in a three-year drought legacy field experiment. We found that drought treatment decreased the microbial alpha diversity compared to the control with no significant differences between monoculture and intercropping systems or bulk soil and rhizosphere soil. Moreover, drought was the main factor affecting microbial community compositions, thereby increasing the abundance of Actinobacteriota, Firmicutes, and Basidiomycota and decreasing the abundance of Proteobacteria, Acidobacteriota, and Ascomycota. Soil labile organic carbon and nitrogen, as well as enzyme activities, were the main environmental factors affecting the bacterial and fungal community compositions. The co-occurrence network analysis revealed that, in response to drought, the intercropping system produced larger, more complex, and more stable soil fungal networks and less stable bacterial networks compared to the monoculture system, even though the microbial diversity was unaffected by the cropping system used. Taken together, drought was the principal factor accounting for variations in microbial communities and changes in soil properties. Even though microbial diversity and structure did not vary significantly in response to drought legacy between monoculture and intercropping systems, the co-occurrence of bacterial and fungal taxa showed notable differences. These findings provided a new strategy to cope with drought stress by optimizing the cropping systems.