Data from: [Long-term ammonium nitrate addition strengthens soil microbial cross-trophic interactions in a Tibetan alpine steppe]

Global nitrogen (N) enrichment is modifying microbial interactions, which can be represented bynetwork complexity. While a number of studies have explored how N addition influences microbial intra-trophic network, its effects on inter-trophic network have rarely been investigated. Here, we examined the effects of 8 years of multi-level N additions(i.e., 0, 1, 2, 4, 8, 16, 24 and 32 g N m-2 year-1) on inter-trophic interactions of soil microbial communities (i.e., protist-fungi, protist-prokaryote and fungi-prokaryote) in a Tibetan alpine steppe. Generally, there was a first increasing and then saturated trend of the complexity of inter-trophic networks along the N-addition gradient, which contrast with the simplified or minimal response of intra-trophic network complexity reported previously. The intensified cross-trophic interactions were mainly explained by increased plant and litter biomass, which indicates that the N-induced increases in carbon supplies may have alleviated microbial energy limitation and thus resulted in more active metabolic processes, consequently stimulating various biotic interactions (e.g., predation, competition and commensalism). Further, the enhanced inter-trophic network relationships were found to associate with increased soil carbon and N mineralization processes. These findings highlight the importance of microbial cross-trophic interactions and indicate that they should be considered in predictions of ecosystem functioning under global N enrichment.