Chronic effects of different fertilization regimes on nirS-type denitrifier communities across the black soil region of Northeast China

Denitrification is one of the major processes causing nitrogen loss from arable soils. This study aimed to investigate the responses of nir S-type denitrifier communities to different chronic fertilization regimes across the black soil region of Northeast China. Soil samples were collected from sites located in the north(NB), middle(MB), and south(SB) of the black soil region of Northeast China,each with four chronic fertilization regimes: no fertilizer(No F), chemical fertilizer(CF), manure(M), and chemical fertilizer plus manure(CFM). Methods of quantitative polymerase chain reaction(q PCR) and Illumina Mi Seq sequencing were applied to assess the abundance and composition of denitrifier communities by targeting the nir S gene. The results showed that the M and CFM regimes significantly increased the abundances of nir S-type denitrifiers compared with No F at the three locations. The majority of nir S sequences were grouped as unclassified denitrifiers, and the different fertilizers induced little variation in the relative abundance of known nir S-type denitrifier taxa. Over 90% of the sequences were shared among the four fertilization regimes at each location,but none of the abundant operational taxonomic units(OTUs) were shared among the three locations. Principal coordinate analysis(PCo A) revealed that the communities of nir S-type denitrifier were separated into three groups that corresponded with their locations.Although similar fertilization regimes did not induce consistent changes in the nir S-type denitrifier communities, soil p H and NO-3-N content simultaneously and significantly influenced the structure of nir S-type denitrifier communities at the three locations. Our results highlight that geographical separation rather than chronic fertilization was the dominant factor determining the nir S-type denitrifier community structures, and similar chronic fertilization regimes did not induce consistent shifts of nir S-type denitrifier communities in the black soils.