In terrestrial ecosystems, deep soils (below 30 cm) are major organic carbon (C) pools. The labile carbon input could alter soil organic carbon (SOC) mineralization, resulting in priming effect (PE), which could be modified by nitrogen (N) availability, however, the underlying mechanism is unclear for deep soils, which complicates the prediction of deep soil C cycling in response to N deposition. A series of N applications with ¹³C labeled glucose was set to investigate the effect of labile C and N on deep SOC mineralization. Microbial biomass, functional community, metabolic efficiency and enzyme activities were examined for their effects on SOC mineralization and PE. During incubation, glucose addition promoted SOC mineralization, resulting in positive PE. The magnitude of PE decreased significantly with increasing N. The N-regulated PE was not dependent on extracellular enzyme activities but was positively correlated with carbon use efficiency and negatively with metabolic quotient. Higher N levels resulted in higher microbial biomass and SOC-derived microbial biomass than lower N levels. These results suggest that the decline in the PE under high N availability was mainly controlled by higher microbial metabolic efficiency which allocated more C for growth. Structural equation modelling also revealed that microbial metabolic efficiency rather than enzyme activities was the main factor regulating the PE. The negative effect of additional N suggests that future N deposition could promote soil C sequestration.

在陆地生态系统中，深层土壤（低于30厘米）是主要的有机碳（C）库。不稳定的碳输入可能会改变土壤有机碳（SOC）的矿化作用，从而产生启动效应（PE），这可能会因氮（N）的有效性而改变，但深层土壤的潜在机制尚不清楚，这使得对深层土壤的预测变得复杂土壤碳循环响应氮沉降。一系列N应用程序，共^13个设置C标记的葡萄糖以研究不稳定的C和N对深层SOC矿化的影响。检查微生物生物量，功能群落，代谢效率和酶活性对SOC矿化和PE的影响。在孵育过程中，添加葡萄糖可促进SOC矿化，从而产生正PE。PE的含量随N的增加而显着降低。N调节的PE不依赖于细胞外酶的活性，而与碳的利用效率呈正相关，与代谢商呈负相关。与较低的氮水平相比，较高的氮水平导致较高的微生物量和SOC衍生的微生物量。这些结果表明，在高氮利用率下，PE的下降主要是由较高的微生物代谢效率控制的，后者为生长分配了更多的C。结构方程模型还表明，微生物代谢效率而非酶活性是调节PE的主要因素。额外的氮的负面影响表明未来氮的沉积可能促进土壤碳的固存。