Increasing aridity is known to influence the diversity and function of soil microbiome. However, how it affects the microbial co-occurrence network are poorly understood, particularly in alpine ecosystem, which is one of the most vulnerable ecosystems. Here, we investigated the co-occurrence networks of soil microbiomes based on 60 sites along a natural aridity gradient across the Tibetan Plateau and evaluated their relationship with soil functionality. We hypothesized that increasing aridity could lead to a reduction in the complexity of microbial networks (e.g., the decreased number of nodes and edges, lower connectance, average degree, clustering coefficient and centralization degree), and this changed network complexity is strongly relate to microbial structure stability (network robustness and vulnerability) and soil functionality. Our results supported the hypothesis that the network complexities of bacteria, fungi and protists decreased along the aridity gradient. Microbial network complexity was significantly correlated with network robustness and vulnerability, suggesting that soil network complexity supports structure stability. Bacterial and fungal network complexities were strongly related to community functional traits (e.g., enzymes activities, carbohydrate and amino acid metabolism, C degradation genes), soil processes (e.g., CO and CH emission, N mineralization) and multifunctionality. This suggests a key relationship of microbial networks to alpine soil functionality, with a more significant impact observed in semi-arid and arid habitats than that in humid and semi-humid habitats. Plants played key roles in driving microbial network through altering soil organic C, with plant diversity having a greater impact in humid habitats, while plant biomass was more influential in semi-arid and arid habitats. Our results indicate that aridity-induced simplification of microbial communities can potentially weaken community stability and alpine soil functionality. Therefore, preserving the complexity of belowground communities is critical for ecosystem management and for predicting the ecological consequences of future aridification.

中文翻译：

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简化的微生物网络降低了高山草地沿自然干旱梯度的微生物结构稳定性和土壤功能

众所周知，干旱加剧会影响土壤微生物组的多样性和功能。然而，人们对它如何影响微生物共生网络知之甚少，特别是在高山生态系统中，这是最脆弱的生态系统之一。在这里，我们研究了青藏高原自然干旱梯度沿线 60 个地点的土壤微生物组共生网络，并评估了它们与土壤功能的关系。我们假设干燥度的增加可能导致微生物网络复杂性的降低（例如，节点和边的数量减少，连接度、平均度、聚类系数和集中度降低），并且这种变化的网络复杂性与微生物网络的复杂性密切相关。结构稳定性（网络稳健性和脆弱性）和土壤功能。我们的结果支持细菌、真菌和原生生物的网络复杂性沿着干旱梯度下降的假设。微生物网络复杂性与网络的稳健性和脆弱性显着相关，表明土壤网络复杂性支持结构稳定性。细菌和真菌网络的复杂性与群落功能特征（例如酶活性、碳水化合物和氨基酸代谢、碳降解基因）、土壤过程（例如二氧化碳和甲烷排放、氮矿化）和多功能性密切相关。这表明微生物网络与高山土壤功能之间存在关键关系，在半干旱和干旱生境中观察到的影响比在潮湿和半湿润生境中更显着。植物通过改变土壤有机碳在驱动微生物网络方面发挥着关键作用，植物多样性在潮湿生境中影响更大，而植物生物量在半干旱和干旱生境中影响更大。我们的结果表明，干旱引起的微生物群落简化可能会削弱群落稳定性和高山土壤功能。因此，保持地下群落的复杂性对于生态系统管理和预测未来干旱化的生态后果至关重要。