轮作模式对冬小麦土壤氨氧化微生物群落多样性和组成的影响

Diversity and composition of ammonia⁃oxidizing archaeal and bacterial communities in rhizosphere and bulk soils of winter wheat in crop rotations

农田温室气体减排已成为农业绿色发展的重要内容,驱动温室气体氧化亚氮(N_(2)O)产生的氨氧化微生物受到了研究者们的广泛关注。为探究轮作模式对土壤氨氧化微生物群落的影响,基于田间定位试验,研究了夏红小豆-冬小麦、夏绿豆-冬小麦、夏花生-冬小麦、夏大豆-冬小麦和夏玉米-冬小麦5种轮作模式中冬小麦根际和非根际土壤氨氧化古菌(AOA)和氨氧化细菌(AOB)的群落组成和多样性变化特征。结果表明:与夏玉米-冬小麦模式相比,豆禾轮作模式增加了根际土中有机碳和硝态氮含量,以及非根际土中全氮和铵态氮含量。豆禾轮作模式降低了非根际土壤中AOA群落的ACE指数和Chao1指数,并显著降低根际土中AOB群落的ACE指数和Chao1指数(P<0.05)。豆禾轮作显著增加AOA群落中泉古菌门(Crenarchaeota)和AOB群落中变形菌门(Proteobacteria)某些类群的相对丰度(P<0.05)。根际土中豆禾轮作模式与麦玉模式的AOA群落结构发生明显分离,而非根际土中豆禾轮作模式与麦玉模式的AOB群落发生分离(P<0.05)。研究结果表明:豆禾轮作种植改变了AOA和AOB的群落结构和多样性,土壤pH值和速效氮含量是驱动AOA和AOB群落结构变化的重要因子,且根际与非根际土壤中氨氧化微生物存在生态位分离。

Farmland is one of the most important sources of greenhouse gas emissions,and as global warming becomes more and more serious,greenhouse gas emissions from farmland are of increasing concern.The vast majority of the land in the North China Plain is dryland,and the main greenhouse gas emitted from dryland is N_(2)O.It is mainly driven by ammonia oxidizers.Ammonia oxidizers convert ammonium(NH_(4)^(+))in the soil to nitrite(NO_(2)^(-)),which is eventually converted to other forms of nitrogen,including N_(2)O.As a result,ammonia oxidizers have received more and more attention from researchers in recent years.Based on a field localization experiment,we investigated the community composition and diversity of ammonia-oxidizing archaea(AOA)and ammonia-oxidizing bacteria(AOB)of winter wheat in rhizosphere and bulk soils in five crop rotations:summer adzuki bean-winter wheat,summer mungbean-winter wheat,summer peanut-winter wheat,summer soybean-winter wheat,and summer maize-winter wheat(as the control group).Results showed that the legume-based rotations increased soil organic carbon and nitrate contents in rhizosphere soils and increased total nitrogen and ammonium contents in bulk soils compared with winter wheat-summer maize,respectively.The legume-based rotations universally reduced Abundance-based Coverage Estimator(ACE)and Chao1 indexes of AOA communities in bulk soils.They significantly reduced ACE and Chao1 indexes of AOB communities in rhizosphere soils(P<0.05).Moreover,the legume-based rotations significantly increased the relative abundance of Crenarchaeota and Proteobacteria for AOA and AOB communities,respectively.Specifically,the relative abundance of OTU58(Crenarchaeota)in the AOA community and the summer adzuki bean-winter wheat and summer mungbean-winter wheat patterns significantly increased the relative abundance of OTU76,OTU95,and OTU3(Proteobacteria)in the AOB community,respectively(P<0.05).The AOA community structures were significantly separated between the legume-based rotations and winter wheat-summer maize in rhizosphere soils.In contrast,the AOB communities were separated between the legume-based rotations and winter wheat-summer maize in bulk soils(P<0.05).Increased soil pH and organic carbon content in rhizosphere soils were important environmental drivers for the separation of AOA community structures.In contrast,changes in total nitrogen and ammonium nitrogen content in bulk soils were the main environmental drivers for the separation of AOB community structures.Our findings indicated that the structure and diversity of AOA and AOB communities were altered by legume-based rotations,and soil pH and available nitrogen content were the driving factors.Additionally,there was an ecological niche separating AOA and AOB in rhizosphere and bulk soils.