Abstract:【Objective】pH and oxygen were the key limiting factors for the ammonia oxidation activity of archaea. The law of competition and adaptation of different archaea ecotypes (soil archaea and marine archaea) to pH and oxygen in complex soils are still unclear.【Method】Ammonia-oxidizing archaea (AOA) was selected as the marine archaea Group1.1a-associated with acid forest soil with pH = 5.40, and the active ammonia-oxidizing archaea were selected as the soil archaea Group 1.1b-associated with alkaline paddy soil with pH = 8.02. After adjusting the pH and oxygen concentration of the mixed soil, a stable isotopic probe microcosm indoor culture experiment was set up to analyze the intensity of soil nitrification. Also, quantitative PCR and 454 high-throughput sequencings were employed to study the effect of different pH and oxygen conditions on the number of soil ammonia-oxidizing archaea and bacteria and also the types of active ammonia-oxidizing microorganisms present.【Result】Compared with zero time, the contents of nitrate nitrogen and ammonium nitrogen had no change at pH3.8; At pH6.0 and 7.6, nitrate nitrogen content increased by 23 times and 19 times, respectively, and the ammonium nitrogen content decreased significantly.The results show that after the soil samples were mixed, there was no nitrification at pH 3.8, while strong nitrification occurred at pH 6.0 and 7.6. Also, the nitrification in a high-oxygen environment was stronger than that in a low-oxygen environment.After substrate culture, the number of oxidizing archaea was increased significantly ; DNA-SIP shows that the active ammonia oxidizing archaea with pH 6.0 and 7.6 were almost all soil archaea Group 1.1b.【Conclusion】 This study reveals that pH rather than oxygen is the main factor affecting nitrification. Although oxygen also has a certain effect on nitrification; in neutral and alkaline soil, soil archaea lineage has greater activity in high O2 and low O2 environment and have more adaptive capacity than marine lineage.