Nitrogen (N) and phosphorus (P) additions reduced soil organic carbon (SOC) contents and stocks in alpine meadows on the Tibetan Plateau. However, little is known about microbial mechanisms behind SOC decline. This study investigated the effects of long‐term N and P additions on microbial community composition and SOC decomposition (C mineralization (C_m), mean resistant times for active C pool (MRT_a), and slow C pool (MRT_s) in alpine meadows. Results showed that the total SOC pool was reduced by 2–9% under N and P additions, of which slow C pool decreased by 3–10%, while active C pool increased by 4–75% compared to the Control. N and P additions shortened MRT_s by 34–40% but prolonged MRT_a by 30–62%. The relative abundance of four bacterial families was related to C_m or MRT_a, while that of most of the fungal families affected SOC decomposition (including C_m, MRT_a, and MRT_s). N and P additions increased fungal diversity, differentially affected microbial community composition and structure through modifying microbial preference, and increasing the abundance of microbes which are capable of decomposing complex carbohydrate. Soil pH, available N, and total P were main factors determining microbial abundances. Microbial changes due to N and P additions accelerated decomposition of recalcitrant SOC, thus led to declines in slow C pool and total SOC pool but increases in active C pool. Therefore, long‐term N and P additions weaken soil functioning as C pool in alpine meadows.

中文翻译：

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氮和磷的添加促进了高寒草甸慢碳库的分解并降低了土壤有机碳的总量

氮（N）和磷（P）的添加降低了青藏高原高寒草甸土壤有机碳（SOC）的含量和储量。然而，关于SOC下降背后的微生物机制知之甚少。这项研究调查了长期添加氮和磷对高寒地区微生物群落组成和SOC分解（碳矿化（C _m），活性碳库（MRT _a）和慢速碳库（MRT _s）的平均抵抗时间）的影响。结果表明，与对照相比，添加氮和磷后总SOC库减少了2–9％，其中慢速C库减少了3–10％，而活性C库增加了4–75％。和缩短的P添加MRT_小号由34-40％，但延长MRT_一个30-62％。四个细菌家族的相对丰度与C _m或MRT _a有关，而大多数真菌家族的相对丰度影响SOC分解（包括C _m，MRT _a和MRT _s）。）。氮和磷的添加增加了真菌的多样性，通过改变微生物的偏好来差异地影响了微生物群落的组成和结构，并增加了能够分解复杂碳水化合物的微生物的含量。土壤pH，有效氮和总磷是决定微生物丰度的主要因素。由于氮和磷的添加引起的微生物变化加速了顽固性SOC的分解，从而导致缓慢的C池和总SOC池下降，而活性C池却增加。因此，长期添加氮和磷会削弱高寒草甸土壤作为碳库的功能。