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Effects of simulated nitrogen deposition on soil nitrogen-transforming microorganisms in Stipa baicalensis steppe
Received:March 05, 2019  
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KeyWord:nitrogen addition;nitrogen-fixation organism;ammonia-oxidizing bacteria;ammonia-oxidizing archaea;denitrifier
Author NameAffiliationE-mail
LIU Hong-mei Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs
Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Tianjin 300191, China 
 
ZHANG Hai-fang Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs
Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Tianjin 300191, China 
 
QIN Jie Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs
Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Tianjin 300191, China 
 
WANG Hui Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs
Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Tianjin 300191, China 
 
ZHANG Yan-jun Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs
Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Tianjin 300191, China 
 
YANG Dian-lin Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs
Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Tianjin 300191, China 
yangdianlin@caas.cn 
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Abstract:
      Grasslands serve as the main sources and sinks of greenhouse gases. Understanding nitrogen(N)transformations in grassland ecosystems would contribute substantially to assessments of their response and feedback to changes in N deposition. To determine the responses of N-transforming microorganism in grassland soil to N deposition, a simulated change in N deposition via N addition(0, 15, 30, 50, 100, 150, 200, and 300 kg N·hm-2·a-1)was set up on Stipa baicalensis steppe in Inner Mongolia in 2010. The abundance of N functional genes was determined using real-time PCR. Results based on samples collected in August 2015 showed that concomitant with an increase in the amount of added N, the abundance of the nifH gene of nitrogen-fixing organisms showed an initial increase and subsequent decrease. Moreover, the addition of ammonium nitrate N(0~200 kg N·hm-2·a-1)promoted an increase in the abundance of the nifH gene. Low-N addition did not have a significant effect on the abundance of the AOB-amoA and AOA-amoA genes of ammonia-oxidizing bacteria, whereas high-N addition(N100, N150, N200, and N300)significantly increased the abundance of the AOB-amoA gene and decreased the abundance of the AOA-amoA gene of ammonia-oxidizing archaea. Similarly, high-N addition(N150, N200, and N300)reduced the abundance of the nirK gene of denitrifying bacteria. Furthermore, in response to an increase in N addition, mowing promoted AOB-driven ammonia oxidation, whereas a lower abundance of denitrifiers mitigated the accumulation of nitrate originating from ammonia oxidation, resulting in a high content of soil nitrate.