Responses of soil microbial community diversity and co-occurrence networks to interspecific interactions in soybean/maize and peanut/maize intercropping systems

Intercropping with legumes can enhance crop productivity by increasing soil nutrient utilization efficiency and soil fertility. However, the influence of interspecific interactions on soil microbial community diversity and co- occurrence networks in different intercropping systems remain unclear. Here, an experiment was conducted on maize intercropping with soybean or peanut in a chernozem soil in northeast China to assess soil chemical properties, enzyme activities and the microbial community in both intercropping systems. Intercropping increased soil N min contents over monoculture in the soybean/maize system with N fertilization but not in the peanut/maize system. Moreover, intercropping decreased the C-acquiring and N-acquiring enzyme activities by 55.1 % and 41.0 %, respectively, compared to monoculture maize in the peanut/maize system but not in the soybean/maize system. Nitrogen application and crop species affected the soil bacterial more than the fungal community R-diversity. Furthermore, intercropping had no effect on microbial community alpha-diversity but changed the bacterial community R-diversity in maize strips in the soybean/maize system and peanut strips in the peanut/maize system with N fertilization. Intercropping increased the complexity and stability of bacterial networks in both soybean/maize and peanut/maize systems with N application. However, the responses of bacterial networks to soybean and peanut intercropping with maize differed without N application. The complexity of microbial networks was driven largely by soil pH and enzyme activities, but the factors driving fungal taxa were more complex than those driving bacterial taxa. The effects of intercropping on soil biological properties (e.g. enzyme activities and microbial community R-diversity) were therefore greater than on chemical properties, and the responses of soil chemical properties, enzyme activities and microbial R-diversity and co- occurrence networks to intercropping systems were dependent on the neighboring crop species. The results have implications for the mechanisms of belowground interactions in legume-based intercropping systems.