Response Of Soil Microbial Community To Long-term Fertilization Regimes In Different Black Soil Locations Of Northeast China

The black soil of northeast China was one of the four largest black soil areas in the world and the important manufacturing base of commodity grain in our country.However,soil quality of this area presented gradually degenenration and the yields of crops become instability due to long-term excessive cultivation and improper management.Amendment of fertilizers was the main agricultural practice for maintaining soil quality and enhancing crop yield.This agronomic practice generally improved soil quality and increased crop yields,and it also directly or indirectly affected soil mircrobial communities,which playing important roles in soil ecosystem.Soil microorganism was crucial driver of soil nutrient cycling and indicator of soil environment variation.The characteristics of soil microorganism were also the important indicators of soil quality and ecological functions.In this study,we collected soil samples from three long-term fertilization experimental sites(located in southern,middle and northern locations of northeast China)across the black soil region of northeastern China,in which four conventional fertilization regimes including non-fertilization(NoF),chemical fertilizer(CF),manure fertilizer(M)and chemical fertilizer plus manure(CFM)were seleceted at each location.In order to explore whether the consistent shifts of microbial communities response to long-term similar fertilization regimes existed in the black soils,on the one hand,qPCR and Illumina MiSeq sequencing were applied to study microbial abundance,diversity and compositions of community,on the other hand,microbial phylogenetic molecular ecological networks were used to reveal the microbial ecological networks of northeast China.The results were showed as follows:1.Proteobacteria,Actinobacteria and Acidobacteria were the dominant bacteria in the black soils of northeast China.Long-term manure addition not only increased soil nutrients,but enhanced the relative abundances of ?-proteobacteria,?-proteobacteria,Bacteroidetes and Firmicutes,which were commoly regarded as copiotrophic bacteria.Amendment of manure induced the values of bacterial diversity became similar,while chemical fertilizer led to these values more discrepant.Long-term different fertilization regimes significantly changed the compositions of bacterial community,but the influencs of fertilization was minor than those of geographical separation.The bacterial communities were closely correlated with soil properties,in which soil pH was the most influential fator in affecting bacterial community compositions.Although the most influential soil properties in bacterial communities were diverse across locations,soil pH and total nitrogen simultaneously had significantly effects on bacterial communities of the black soils.2.Ascomycota was the dominant fungal taxa in black soils of northeast China.Long-term chemical fertilization obviously increased the abundances of potential plant pathogenic fungi,i.e.Fusarium,while manure addition contributed to inhibite the potential plant pathogenic fungi,i.e.Phoma,Fusarium,and Cryptococcus,but promoted growth of beneficial soil fungi,i.e.Mortierella.Similar to the bacterial community strucutres,fungal communities of northeast China still distributed according to sampling location.Long-term had significantly influences on fungal communites in some extent,but similar fertilization regimes presented different effects on fungal communities across three locations.Soil pH was still main influential soil property in determining the whole and indivual fungal communities,but soil total phosphorus,ammonium nitrogen and total nitrogen were the most important factors on fungal communities of SB,MB and NB,respectively.3.Proteobacteria dominanted the diazotrophic communites in the black soils of northeast China,but the abundance of genera affiliated with proteobacteria obviously differed across three locations.Skermanella was the most abundant in the SB,but Bradyrhizobium was the dominant diazotrphic genera in the middle and northern locaitons.Long-term chemical and manure fertilization significantly decreased the abundance of free-living diazotrihps,i.e.Anabaena,while promoted the growth of symbiotic diazotrophs,i.e.Bradyrhizobium.Long-term inorganic or organic fertilizers addition not only significantly decreased the diazotrophic diversity,but markedly changed the community strucutres of diazotrophs.Similar to bacterial and fungi,geographical separation rather than fertilization was the most dominant factor in affecting diazotrophic communities and all the examined soil properties significantly influenced the whole diazotrophic community structres expert from soil total potassium.Although the most influential soil properties varied across three locations,soil total carbon,total nitrogen and available phosphorus simultaneously obviously impacted diazotrophic communities of the black soils.4.Proteobacteria was the dominant denitrifying bacteria in the black soils of northeast China.However,the abundances of denitrifying bacterial genera affiliated with proteobacteria obviously differed across three locations,in which Rhodanobacter was dominant in SB while Bradyrhizobium was the most abundant denitrifying bacteria in MB and NB.Long-term fertilization addition,especially manure,significantly increased the gene copies of denitrifying bacteria,which was most influenced by soil total nitrogen and total phosphorus.Chemical fertilization regimes had no obvious influence on the denitrifying bacterial diversity of SB,but significantly decreased index in MB and NB.The strucutres of denitrifying bacterial community also mainly separated according to the sampling loactions,and all the examined soil properties significantly influenced the whole denitrifying bacterial communities.The shifts of soil properties response to long-term different fertilization changed the denitrifying bacterial communities within individual location in some extent,and soil carbon and nitrogen nutrients simultaneously and significantly impacted structures of denitrifying bacteria in the whole and individual location.5.The phylogenetic molecular ecological networks of bacteria and fungi of northeast China were constructed based on the Random Matrix Theory(RMT).The topological parameters of networks showed that the bacterial network of MB seemed less stable,while the fungal network structure of SB seemed to be more easily disturbed by shifts of external environments.The bacterial network of SB was slightly more complicated than those of MB and NB,and the proportions of competitive relationship among species in three locations were similar.The fungal network of NB was more complicated than the other locations,and existed more competitions relationship among species.The correlations of network connectivity and soil properties showed that soil pH and total phosphorus simultaneously and significantly influenced the structures of three bacteria networks,while soil pH and total nitrogen simultaneously and significantly impacted the structures of three fungal networks.Therefore,soil pH was the key factor in determining microbial network structures in the black soils of northeast China.