Effects Of Nighttime Free Air Temperature Increased And Nitrogen Application On Soil Fungi Diversity

Climate warming and excessive application of nitrogen fertilizer have become a serious and important issue in China.The impact of global warming on crop systems,especially the effects of soil and microorganisms in soil,has become a research focus and hotspot in the field of global warming and microbiology.Winter wheat is an important grain crop in China.The temperature change and nitrogen application rate greatly affect the growth and development,yield and quality of winter wheat.Previous studies on the nighttime warming of winter wheat mainly focus on the above-ground part of the study,and there were few studies on the changes in the underground part,especially the microbial community.In this study,we set up the night warming treatment before the flowering stage of winter wheat(NW:night warming;AMB:ambient)by the free air temperature inereased system of farmland(FATI),and three levels of nitrogen fertilizer(N1,N2 and N3 mean 150,225,375 kg ha-1 for nitrogen,respectively),to explore the synergistic relationship between soil fungal microbial community structure,diversity and environment with the help of high-throughput sequencing at Jiangpu farm,Nanjing city,Jiangsu Province between 2016 to 2018 year.From the point of view of soil-fungus-crop,we systematically studied the changes of community structure of fungal microorganisms,the relationship between fungal microorganisms and nutrients,and the ecological mechanism of response to warming and nitrogen application,providing theoretical basis for rational fertilization and evaluation of nitrogen utilization efficiency under future climate warming.The main conclusions of the study are as follows:1)The temperature increase of the free air temperature inereased system is 1-2?,which is expressed as ground surface temperature>canopy temperature>middle temperature of the canopy>5cm belowground temperature.Soil water content and soil pH were significantly decreased under night warming,and soil ammonium nitrogen and nitrate nitrogen contents were increased by 13.21%and 2.17%,respectively.With the increase of nitrogen application rate,the contents of available nutrients(NH4+-N,NO3--N)in soil showed an increasing trend,and the effects of night warming and different nitrogen application rates on soil total nitrogen and organic matter were not significant.2)According to the high-throughput sequencing platform analysis,there was no significant difference in the sequence length of soil fungi between different treatments within the range of 401-460bp when the temperature was increased at night and the nitrogen was applied at different rates.The number of soil fungus OTU was increased under different nitrogen application.The OTU number of soil fungi under N2 treatment was significantly lower than that under N1 and N3 treatment.On the phylum level,Ascomycota,unclassified k-fungi,Zygomycota and Basidiomycota comprise more than 80%of the sequences.At the genus level,the soil dominant groups mainly include Diatrype,Mortierella and Mucor.The response of bacterial flora at different phylum and genus levels to warming and nitrogen application was different.Night warming reduced the richness,evenness and diversity of soil fungi community,and reduced the Chao index,Ace index,Shannoneven index,and Simposoneven index by 10.56%,6.38%,42.00%and 10.82%,respectively.3)The relationship between soil fungi species is closely related to soil environmental changes.The abundance of Ascomycota and Zygomycota was positively correlated with soil organic matter content,but negatively correlated with soil temperature,soil moisture and soil available nitrogen content.Temperature,soil moisture,available nitrogen and organic matter are the key factors that dominate the changes of soil fungal community structure in winter wheat.Organic matter and temperature were positively correlated with fungal community diversity,while pH,available nitrogen,soil moisture content and nitrogen fertilizer application level were negatively correlated with fungal community diversity.Structural equation model analysis showed that the direct effect of night warming and nitrogen application on soil fungal community diversity was mainly temperature change.The direct effect of nitrogen application on soil fungal community was small and did not reach significant level.However,soil physical and chemical properties were changed by night warming and nitrogen application,and indirect negative effects on fungal community diversity were produced.Soil moisture,available nitrogen content and root biomass were the main negative factors.