Nitrogen deposition at rate not more than 50 kg ha−1 year−1 is generally considered to stimulate soil nitrifying and denitrifying microorganisms via increases in soil nitrogen content. However, this phenomenon in alpine ecosystems remains largely untested. We conducted an 8-year nitrogen deposition experiment on the Qinghai–Tibetan Plateau, with four nitrogen deposition rates of 10 (atmospheric deposition), 20, 30, and 50 kg ha−1 year−1. The abundances of two nitrifying genes and four denitrifying genes and the N2O emission rate initially increased and subsequently decreased as the nitrogen deposition rate increased. The observed decrease in these indices at the rate of 50 kg ha−1 year−1 was caused by the toxicity of excessive NH4+. Our study demonstrates the vulnerability of alpine microorganisms under global changes.

中文翻译：

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青藏高原土壤硝化反硝化微生物对氮沉降的敏感性

通常认为以不超过50 kg ha-1 year-1的速率沉积氮能够通过增加土壤中的氮含量来刺激土壤硝化和反硝化微生物。但是，高山生态系统中的这种现象在很大程度上尚未得到检验。我们在青藏高原进行了为期8年的氮沉降试验，其中4种氮沉降速率分别为10（大气沉积），20、30和50 kg ha-1年-1。随着氮沉降速率的增加，两个硝化基因和四个反硝化基因的丰度和N2O排放率先增加后减少。观察到这些指数以50千克ha-1年-1的速度下降是由于过量NH4 +的毒性所致。我们的研究表明了全球变化下高山微生物的脆弱性。