Information about the interactions between microbial carbon (C), nitrogen (N), and phosphorus (P) mineralization and nutrient inputs will improve our understanding of the effects of global change on soil biogeochemical cycling and ecosystem function. In this study, we explored how N, P, and NP inputs, when applied at low rates (50 kg ha^–1 year^–1) for seven years, affected the microbial community in an acidic, strongly weathered, red clay soil in a subtropical conifer plantation. N and P inputs regulate microbial communities holistically through influencing soil resources (bottom-up), such as the C and nutrient supply, and predators, such as protists (top-down). We observed that N, P, and NP inputs caused changes in the protist community, which then affected bacterial diversity rather than fungal diversity. The increases in the protist diversity that resulted from the P and NP inputs were associated with increases in the relative abundance of Calditrichaeota, which is involved in C-mineralization, and decreases in the relative abundance of Marinimicrobia, which is involved in N-mineralization. The N and NP inputs caused the soil to become more acidic, exacerbated the microbial C limitation, and reduced the overall microbial functional diversity to carry out C, N, and P mineralisation. We conclude that the nutrient supply directly impacted the C-, N-, and P-mineralising microbial communities (bottom-up), and directly and indirectly affected soil protists (top-down).

有关微生物碳（C）、氮（N）和磷（P）矿化与养分输入之间相互作用的信息将提高我们对全球变化对土壤生物地球化学循环和生态系统功能影响的理解。在这项研究中，我们探讨了连续七年低施用量（50 kg ha ^–1年^{–1 ）氮、磷和氮磷投入量如何影响酸性、强风化红}粘土中的微生物群落。亚热带针叶树人工林。氮和磷输入通过影响土壤资源（自下而上）（例如碳和养分供应）以及捕食者（例如原生生物）（自上而下）来整体调节微生物群落。我们观察到 N、P 和 NP 输入引起了原生生物群落的变化，从而影响了细菌多样性而不是真菌多样性。由 P 和 NP 输入导致的原生生物多样性的增加与参与 C 矿化的Calditrichaeota相对丰度的增加以及参与 N 矿化的Marinimicrobia相对丰度的减少有关。N和NP的输入导致土壤变得更加酸性，加剧了微生物C的限制，并降低了进行C、N和P矿化的微生物的整体功能多样性。我们得出的结论是，养分供应直接影响 C、N 和 P 矿化微生物群落（自下而上），并直接和间接影响土壤原生生物（自上而下）。