Sensitivity of soil nitrifying and denitrifying microorganisms to nitrogen deposition on the Qinghai–Tibetan plateau
Minjie Xu, Tingting Li, Wei Liu, Junjun Ding, Lili Gao, Xingguo Han, Ximei Zhang
Abstract
Abstract Purpose 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. Methods 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 . Results The abundances of two nitrifying genes and four denitrifying genes and the N 2 O 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 NH 4 + . Conclusions Our study demonstrates the vulnerability of alpine microorganisms under global changes.