Denitrification is the main microbial N loss pathway on the Qinghai-Tibet Plateau above an elevation of 5000 m

• Published in: The Science of the total environment 2019-12, Vol.696, p.133852, Article 133852
• Main Authors: Wang, Shanyun, Liu, Weiyue, Zhao, Siyan, Wang, Cheng, Zhuang, Linjie, Liu, Lu, Wang, Weidong, Lu, Yonglong, Li, Fangbai, Zhu, Guibing
• Format: Article
• Language: English
• Subjects: Altitude; Anammox; DAMO; Denitrification; Environmental Monitoring; Methane; N cycle; Nitrates; Nitrogen; Oxidation-Reduction; Qinghai-Tibet plateau; Soil Microbiology; Soil profile; Tibet; Wetlands
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.133852

Soil nitrogen (N) deficiency is the major factor contributing to low primary productivity on the Qinghai-Tibet Plateau. However, most of our understanding of N cycling is still based on human disturbed environments, and the microbial mechanisms governing N loss in low primary productivity environment remain unclear. This study explores three microbial N loss pathways in eight wetland and dryland soil profiles from the Qinghai-Tibet Plateau, at an elevation of above 5000 m with little human activity, using 15N isotopic tracing slurry technology, quantitative PCR, and high-throughput sequencing. No denitrifying anaerobic methane oxidation was detected. Anammox occurred in two of the wetland (n = 4) and dryland (n = 4) soil profiles, while denitrification widely occurred and was the dominant N loss pathway in all samples. Where denitrification and anammox co-occurred, both abundance and activity were higher in wetland than in dryland soils and higher in surface than in subsurface soils. In comparison with non-anammox sites, nitrate levels initiate anammox-related N cycling. High-throughput sequencing and network analysis of nirK, nirS, nosZ, and hzsB gene communities showed that Bradyrhizobiaceae (a family of rhizobia) may play a dominant role in N loss pathways in this region. Given the geological evolution and relatively undisturbed habitat, these findings strongly suggest that denitrification is the dominant N loss pathway in terrestrial habitats of the Qing-Tibet Plateau with minimal anthropogenic activity. [Display omitted] •Denitrification widely dominate N-loss on the Qinghai-Tibet Plateau above 5000 m.•Anammox contribute 5.5–17.4% N-loss in Naqu, don't widely occur.•NO3− levels initiate anammox-related N cycling.•Bradyrhizobiaceae is a key taxa in N-loss gene communities.•Damo bacterial abundance and activity was undetected.