A laboratory incubation experiment was conducted using 15 NH 4 NO 3 or NH 4 15 NO 3 (0.1 mg N g −1 soil (0.1 N) and 0.5 mg N g −1 soil (0.5 N)) labeled soil, with or without litter addition. The newly synthesized amino sugars derived from exogenous nitrogen ( 15 N) were differentiated and quantified using a gas chromatography/mass spectrometry technique. Litter addition enhanced the incorporation of deposited N (exogenous N) to microbial residues (amino sugars), while the contribution of bacterial and fungal residues to N transformation varied at different incubation stages. There was a succession from fungal to bacterial residues after the deposited N addition, while the contribution of fungal residues to the NO 3 − transformation increased at the later stage of litter decomposition. The contents of total 15 N ( 15 NH 4 + + 15 NO 3 − ) derived microbial residues in the low N (litter + 0.1 N) treatment were similar to that in the high N (litter + 0.5 N) treatment, which indicated that microorganisms had a saturation effect on the utilization of deposited N at different concentrations. Moreover, there was a preferential uptake of NH 4 + than NO 3 − by microorganisms, while the strategy of microorganisms to utilize different forms of N depended upon the deposited N concentration. When the deposited N concentration was low, the microorganisms would have no choice but to use NO 3 − , while when the deposited N concentration was high, the microorganisms would selectively utilize NH 4 + and decrease the utilization of NO 3 − . Our study indicated that with the increase in atmospheric N deposition in the future, selective utilization of deposited NH 4 + and NO 3 − by microorganisms may increase the potential losses of NO 3 − from forest soil, especially in China, where the NH 4 + /NO 3 − ratio has recently decreased in atmospheric deposition.

中文翻译：

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温带森林土壤中沉积氮的微生物利用策略

使用 15 NH 4 NO 3 或 NH 4 15 NO 3 (0.1 mg N g -1 土壤 (0.1 N) 和 0.5 mg N g -1 土壤 (0.5 N)) 标记土壤进行实验室孵化实验，有或没有垃圾添加。使用气相色谱/质谱技术对源自外源氮 (15 N) 的新合成氨基糖进行区分和定量。垫料添加增强了沉积的氮（外源氮）与微生物残留物（氨基糖）的结合，而细菌和真菌残留物对氮转化的贡献在不同的孵化阶段有所不同。在沉积氮添加后，真菌残留向细菌残留连续发生，而在凋落物分解后期，真菌残留对NO 3 - 转化的贡献增加。低氮（凋落物+0.1 N）处理中总15 N（ 15 NH 4 + + 15 NO 3 - ）来源微生物残留量与高氮（凋落物+0.5 N）处理相似，表明微生物对不同浓度沉积氮的利用具有饱和效应。此外，微生物对NH 4 + 的吸收高于NO 3 - ，而微生物利用不同形式的N 的策略取决于沉积的N 浓度。当沉积N浓度低时，微生物只能使用NO 3 - ，而当沉积N浓度高时，微生物会选择性地利用NH 4 + ，降低NO 3 - 的利用率。我们的研究表明，随着未来大气氮沉降的增加，