Ammonia-Oxidizing Bacteria and Archaea: Response to Simulated Climate Warming and Nitrogen Supplementation

Ammonia oxidation, the first and rate-limiting step of the nitrification process, is driven by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Numerous studies on the response of aboveground plant and soil microbial communities to climate change have been conducted, but the effects of climate warming and nitrogen (N) supplementation on the abundance, community composition, and diversity of AOA and AOB in arid and semiarid steppe ecosystem remain elusive. In this study, we examined these effects on soil samples from the Inner Mongolia desert steppe after 11 consecutive years of simulated climate warming and N supplementation (ammonium nitrate), using real-time quantitative polymerase chain reaction analysis and high throughput sequencing technique. We observed that the amoA abundance of AOA outnumbered that of AOB in this desert steppe, with N supplementation having a significant effect on amoA abundance. The effect of climate warming on the amoA abundance of AOA or AOB depended on soil depth. Eleven years of simulated climate warming and N supplementation had varying effects on the amoA abundance of AOA and AOB. Nitrogen supplementation shifted ammonia-oxidizing bacterial community structure, increased potential nitrification rates, and affected ammonia-oxidizing microbial a diversity at topsoil. The dominating factors shaping AOB community structure among the treatments were NH4+-N, NO3--N, and pH, whereas pH was the significant factor in shaping AOA community structure. Our results indicate that N supplementation might be the driving factor aiding oxidation of ammonia at topsoil of arid and semiarid steppe ecosystem.