Response Of Soil Microbial To Nitrogen Addition In Moss Biological Crusts Of The Southern Gurbantunggut Desert

The increase in atmospheric nitrogen(N)deposition can alter the structure and diversity of soil microbial communities,which in turn affects the processes and functions of the ecosystem.In desert ecosystems,studying the effect of N deposition on soil microbial communities of moss crust,can supplement the research results of the effects of N deposition on desert biological crusts,and promote the optimal management and reasonable protection of desert ecosystems.The study area is located in the southern Gurbantunggut Desert,the test set 4 N treatment levels:blank control(N0,0g N·m^-2·a^-1),low-N treatment(LN,1.8g N·m^-2·a^-1),medium-N treatment(MN,3.6g N·m^-2·a^-1),high-N treatment(HN,7.2g N·m^-2·a^-1),on the one hand,to analyze the effects of N deposition on moss crusts soil physicochemical properties and microbial biomass,on the other hand,using high-throughput sequencing technology,to analyze the effects of N deposition on moss crusts soil bacterial and fungi community structure and diversity.The main results are as follows:(1)N addition treatment reduced the soil pH value,but significantly increased the content of soil TN,TP,AN,and AP.In summer,N addition significantly altered soil SOC content,indicating that short-term effective N addition changed the stability of soil carbon.At the same time,in different seasons,soil SWC,pH,and SOC were significantly different,SWC content showed summer<spring<winter,pH value showed spring<winter<summer,SOC content showed summer<winter<spring,while TN,TP,AN,and AP had no significant difference between seasons.N addition and seasonal changes are significantly affected the soil microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN),showed as MN addition promotion but HN addition inhibition,in summer,MBC and MBN reached the maximum.(2)In the moss crusts system,the number of soil bacteria species was between1529-2381,the number of soil fungi species was in 323-758.In general,the number of bacteria species was significantly higher than that in the fungal species,at the same time,we found no significant change in the number of community species before and after N addition.(3)The early stage of moss crust development,soil bacterial diversity index was no significant difference in different N treatment levels,Shannon diversity index was increased with the seasonal change,and reached the maximum in winter,while the Simpson index showed a single-peak seasonal change,which increased first and then decreased with the seasonal change,and reached the maximum in summer.However,at the later stage of development,the diversity index was significantly decreased under MN and HN treatments,and also showed a single-peak seasonal variation,and reached the maximum in summer.The dominant phylum in the soil bacterial community were Proteobacteria(28.0%-66.29%),Actinobacteria(6.70%-34.95%),Bacteroidetes(4.36%-16.29%),Acidobacteria(3.57%-15.70%),Chloroflexi(1.54%-15.83%),and Firmicutes(0.77%-9.60%),the relative abundance accounts for about 85.46%-94.71%of the total.In summer,the bacterial relative abundance was significantly different under different N treatment levels;in spring and winter,compared with N0 treatment,the relative abundance of the dominant bacteria in the N treatment group did not significantlychanged;at the same time,the bacterial relative abundance was varied significantly between seasons,the soil bacterial community composition was significantly affected by soil SOC,SWC,AK,and pH,while the diversity of bacterial community was significantly affected by soil pH,SWC,TP,AP,AN,and NO₃^--N.(4)The effect of N addition on the soil fungi community diversity showed significant seasonal differences,in spring and winter,N addition significantly increased diversity index,in contrast,in summer,N addition significantly decreased diversity index.In the early stage of development,soil fungi community diversity index reached maximum in winter;in the later development period,soil fungi community diversity index reached maximum in spring;at the same time,N application changed the seasonal characteristics of fungal diversity.Ascomycota(48.46%-95.62%),Basidiomycota(2.40%-15.53%),and Mortierellomycota(0.34%-20.51%)were dominant phylum in fungi community,the relative abundance accounted for about 73.74%-99.82%of the total.The relative abundance of fungi was significantly different between different N treatment levels and seasons,the fungi community composition and diversity were significantly affected by soil SOC,SWC,TP,AP,AK,and pH.(5)N addition and seasonal changes affected the ecological interaction network structure of soil bacterial and fungal communities and the interaction between the communities.The specific performance as:N addition reduced the complexity of the network structure;the network complexity varied with seasonal changes,in the order of summer>winter>spring,indicating that as the length of the test increases,the network complexity is lower.