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.

全球氮（N）富集正改变微生物间的相互作用，这种作用可通过网络复杂度来表征。尽管已有多项研究探讨了氮添加对微生物营养内网络的影响，但对其营养间网络的作用却鲜有研究。本研究分析了8年多水平氮添加（即0、1、2、4、8、16、24和32 g N m⁻² year⁻¹）对西藏高寒草原土壤微生物群落营养间相互作用（即原生生物-真菌、原生生物-原核生物及真菌-原核生物）的影响。总体而言，沿氮添加梯度，营养间网络复杂度呈现先上升后饱和的趋势，这与先前报道的营养内网络复杂度简化或响应微弱的结果形成对比。跨营养级相互作用的增强主要可由植物及凋落物生物量的增加解释，这表明氮诱导的碳供应增加可能缓解了微生物的能量限制，从而促进了更活跃的代谢过程，进而刺激了多种生物相互作用（如捕食、竞争及共生）。此外，研究发现增强的营养间网络关系与土壤碳和氮矿化过程的增强相关。这些发现凸显了微生物跨营养级相互作用的重要性，并表明在预测全球氮富集下的生态系统功能时应考虑这些相互作用。