Study On The Nitrifiers In The Rhizosphere Soils Of Caragana Spp. Across Sandy Land Of Northern China

As the key process to soil nitrogen cycle,nitrification is associated with soil mineralization,denitrification and anammox,and is also crucial to the microbial oxidation process.Nitrification can be affected by different soil properties,such as pH,temperature,moisture,ammonium nitrogen and organic matter content,which are also generally considered to be the important environmental factors shaping the community composition of nitrifiers.Sandy soils are generally thought to be nutrient poor and water shortage,and at present,it is still unclear that the distribution,diversity of nitrifiers and their relative contribution to the nitrification in this environment.Besides,there is limited information about the research of nitrifiers in the rhizosphere soils of Caragana spp.In this study,the abundance,diversity and relative contributions to ammonia oxidization of ammonia-oxidizing Archaea,Bacteria and Fungi at rhizosphere of Caragana spp.plants in sandy soil were investigated with the method of potential nitrification rates(PNRs),quantitative PCR assay and Hi-seq sequencing.Here,the main results of this study were described as the followings:1.The abundance of AOA and AOB gene showed wide variation at studied five desert sites,ranging from 2.64×105-4.02×107 and 2.07×106-1.78×107 copies per gram of dry soil,respectively.The amoA gene copies of AOA outnumbered the 16 S rRNA of AOB at ZGT,NM and YL.In contrast,numerical dominance of AOB over AOA at MQ site.And the relative abundance of AOA and AOB showed no obvious trend at YC site.The abundance of ammonia-oxidizing microbiology showed a significantly negative correlation with pH,while a positive correlation with TN,NH4+ and organic matter.It showed that the abundance of AOA and AOB were affected by pH,TN,NH4+ and organic matter.2.Surface soils(2-10 cm)at the five sampling sites showed the highest total PNRs among all the sampling depths,and total PNRs declined with depth.Total PNRs at rhizosphere of Caragana spp.plants is higher than total PNRs at bulk soil(non-rhizosphere)at the same depth in every site.In conclusion,total PNRs showed a significantly negative correlation with TN,NH4+,OM and the abundance of nitrifiers,while a significantly positive correlation with pH,NO3-,UA.This results indicated that soil total PNRs were influenced by pH,TN,OM and UA.3.At ZGT site,the PNRs of fungi showed the highest PNRs,the PNRs of AOA was secondary and the PNRs of AOB was lowest.While the PNRs of AOA showed the highest PNRs,the PNRs of AOB and the PNRs of Fungi showed no obvious trend at NM,YL,YC,MQ site.4.Phylogenetic analysis demonstrated that AOA affiliated to GroupI.1b and Group I.1c of Thaumarchaeota,AOB affiliated to Nitrosospira and Nitrosomonas,and Fungi affiliated to Streptophyta and Ascomycota.Redundancy analysis(RDA)was performed to identify the correlation between soil geochemical characteristics and composition of AOA and AOB community.It is obvious that SWC was the main factor which influenced the community composition of AOA,and SWC,NH4+ were the two factor which influenced the community composition of AOB,in addition,pH,SWC,TN and NH4+ were the four main factors which influenced the community composition of fungi.5.AOA were successful enriched from YC site and affiliated to Thaumarchaeota based on amoA gene.In addition,AOA are an aciduric,mesophilic ammonia oxidization microbiology.