Abstract: Soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are the key microorganisms for soil nitrification. In this study,surface soil sampled from three types of grassland,including desert steppe,typical steppe,and meadow steppe in Inner Mongolia,we measured the abundance of AOA and AOB using fluorescence quantitative PCR (qPCR) and analyzed the relationship between grassland type and environmental factors. The results showed a significant difference in the abundance of AOA among the three types of grassland in Inner Mongolia,which is typical steppe>desert steppe>meadow steppe. But no significant differences were found in the abundance of AOB among the three types of grassland. The abundance of AOA in the same type of grassland is 31~147 times that of AOB. The abundance of AOA was positively correlated with elevation,total organic carbon(TOC),underground biomass,the abundance of bacteria and fungi. The mean annual temperature(MAT) and bulk density were negatively correlated with soil pH. The abundance of AOB was positively correlated with bacteria fungi,TOC,MBC,MBN. MAT was negatively correlated with pH. The difference of the abundance of AOA is greater than that of AOB in different spatial scales. The results are helpful to explicate the reason of productivity difference in different types of grassland and could provide data supports for the improvement of grassland soil nitrogen cycle models.

Key words: AOB, AOA, Typical grassland, Meadow grassland, Desert grassland

摘要： 氨氧化细菌（Ammonia-oxidizing bacteria，AOB）和氨氧化古菌（Ammonia-oxidizing archaea，AOA）是参与土壤硝化过程的关键微生物。本文以内蒙古3种草地类型（荒漠草原、典型草原和草甸草原）表层土壤为研究对象，利用qPCR技术测定土壤AOA，AOB的丰度，研究其与不同类型草地生物和环境因子之间的关系。结果表明：不同草地类型间AOA的丰度存在显著差异，典型草原>荒漠草原>草甸草原；但是AOB的丰度在不同草地类型间差异不显著。同一类型草地土壤AOA的丰度是AOB丰度的31~147倍。AOA丰度与海拔高度、土壤总有机碳含量、植物地下生物量、细菌和真菌的丰度呈显著正相关关系，与年均温、土壤容重和土壤pH值呈显著负相关关系；AOB丰度与细菌和真菌丰度、土壤总有机碳、微生物生物量碳/氮呈显著正相关关系，与年均温、土壤pH值呈显著负相关关系。AOA的丰度在不同空间尺度存在较大差异，而AOB丰度的差异较小。本研究结果有助于解释不同草地类型生产力差异的原因，为全球气候变化背景下草地土壤氮循环模型的完善提供数据支持。

关键词: 氨氧化细菌, 氨氧化古菌, 典型草原, 荒漠草原, 草甸草原