An understanding of the priming effect (PE), i.e. the effects of carbon (C) and nitrogen (N) inputs on the priming of pre-existing soil organic C mineralization, is fundamental to predicting future soil C cycling and climate feedback. Since the direction and magnitude of the PE depend on the turnover of microbial biomass C and N, we evaluated the PE in relation to pre-existing biomass C and N using dual labeling of glucose ¹³C and mineral ¹⁵N for Japanese moderately acidic (pH of 5.0) cedar and strongly acidic (pH of 4.1) cypress soils. The addition of C only to the cedar soil caused no PE with no change in biomass turnover relative to the control without C or N additions. The addition of N with C caused a positive PE, leading to a net loss of soil C stocks, and decreased pre-existing biomass N due to the higher turnover of biomass N relative to the control. The result for the cedar soil was in line with the stoichiometric decomposition theory but not with microbial N mining theory. By contrast, the addition of C only and both C and N to the cypress soil caused a negative PE. Our study revealed that increasing the pre-existing biomass N turnover can lead to a positive PE, accelerating net soil C loss, when the soil pH does not limit microbial activities.

了解引发效应（PE），即碳（C）和氮（N）输入对已存在的土壤有机C矿化引发的影响，对于预测未来的土壤C循环和气候反馈至关重要。由于PE的方向和大小取决于微生物生物量C和N的周转，因此我们使用葡萄糖¹³ C和矿物质^15的双重标记评估了PE与现有生物量C和N的关系。N用于日本中度酸度（pH值为5.0）的雪松和强酸度（pH值为4.1）的柏树土壤。与没有添加碳或氮的对照相比，仅向雪松土壤中添加碳不会引起PE，且不会改变生物量的变化。氮与碳的添加导致PE值为正，导致土壤碳储量净损失，并且由于相对于对照而言，生物量N的营业额较高，因此减少了原有生物量N的含量。雪松土壤的结果符合化学计量分解理论，但不符合微生物氮的开采理论。相比之下，仅添加C以及将C和N都添加到柏树土壤中会导致PE值为负。我们的研究表明，当土壤pH值不限制微生物活动时，增加原有生物量N的周转量可导致PE正值，加速土壤净C损失。