Microbial Status Of Soil And Air With Different Green Spaces And Seasons

Green space is an important part of the ecosystem.At present,with the accelerating process of urbanization,and the more and more prominent problems of urban ecological environment,the ecological benefits of green space have been paid more and more attention.This paper mainly studied the ecological role of green space in two aspects including air bacteriostasis and soil microbial diversity protection in order to explore the seasonal distribution characteristics and influencing factors of soil and air microorganisms in different green space environments,and explore the types of green space that can minimize or suppress environmental air microorganisms under the condition of ensuring soil microbial diversity.This paper took 8 green spaces with typical vegetation characteristics in the South Campus of Northwest Agriculture and Forestry University as the research objects,using high-throughput sequencing method and plate sedimentation method,analyzed and studied the seasonal variation and influencing factors of soil microbial and air microbial distribution characteristics in different vegetation types of green space.Moreover,it comprehensively considered the performance of green space in soil microbial diversity protection and green space air bacteriostasis.The research results showed that:(1)Both vegetation type and season have certain influence on the composition and structure of soil microbial community.The compositional characteristics of soil bacterial and fungal communities in spring and autumn in the 8 green spaces were basically the same,and only the relative abundances differed,and the differences in abundance in autumn were significantly greater than those in spring.The dominant and subdominant groups of soil bacteria at the phylum classification level were Proteobacteria and Acidobacteria,respectively;the dominant and subdominant groups of soil fungi at the phylum classification level in spring were Ascomycota and Mortierella,respectively,and in autumn were Ascomycota and Basidiomycota,respectively.(2)Both vegetation types and seasons have certain effects on soil microbial diversity characteristics.The difference of soil microbial diversity in autumn was more obvious than that in spring.Soil bacterial diversity was the highest in lawn(L),the lowest in arbor-shrub-herb forest(ASH)and coniferous forest(C),and the second lowest in intensive shrub(IS)and coniferous and broad-leaved mixed forest(CBL).Soil fungal richness was the highest in coniferous and broad-leaved mixed forest(CBL),and the lowest in arbor-shrub-herb forest(ASH)and lawn(L).(3)The differences in soil microbial diversity and microbial species at the phylum classification level are affected to some extent by soil physicochemical factors.The diversity and uniformity of soil bacteria and soil fungi(shannon and simpson)were less affected by soil physicochemical properties,while soil bacterial and soil fungal richness(chao1 and ACE)were mainly affected by total phosphorus,alkali-hydrolyzed nitrogen,available potassium,p H and soil water content.(4)There are seasonal differences in the air microbial concentration of different vegetation types and vertical structures of green spaces.The air bacteria concentration was the highest in spring and the lowest in autumn,and the air fungal concentration was the highest in spring and the lowest in summer.According to the vegetation type,the concentration of air bacteria and fungi in coniferous forest was basically the lowest among all green spaces in one year.According to the vertical structure,the air bacteria concentration of tree-grass structure was basically the lowest among all structures,while the air fungal concentration of shrub structure and tree-grass structure was basically the lowest among all structures.(5)Green spaces with different vegetation types and vertical structures have different inhibitory effects on air bacteria and air fungi,and there are seasonal differences.On the whole,green space had a strong inhibitory effect on air bacteria,but it can breed fungi.Coniferous forest had the most stable inhibitory effect on bacteria,and it had a very slight inhibitory effect on air fungi;The average annual bacteriostatic effect of air bacteria in green spaces with different vertical structures was arbor-grass structure > shrub structure >grass structure,while the arbor-shrub-grass structure showed the effect of increasing bacteria.The average annual fungi inhibition rate of each vertical green space was negative,and the fungi-enhancing effect was arbor-grass > shrub > grass.The tree-shrub-grass structure is the most easy to breed fungus.(6)Air microbial concentration is affected by various environmental factors and soil microbial diversity,among which temperature is the most important factor.Temperature and soil microbial richness index was negatively correlated with airborne microbial concentration.Humidity was negatively correlated with air bacterial concentration but positively correlated with air fungal concentration.Air pressure was positively correlated with airborne microbial concentration.Wind speed was negatively correlated with air fungal concentration.The air bacterial concentration was negatively correlated with the soil bacterial diversity index.The air fungal concentration was negatively correlated with Simpson’s diversity index.(7)Comprehensively considering the green space soil microbial diversity index and air microbial concentration,the paper preliminarily conducted a comprehensive evaluation of the ecological benefits of 8 green spaces with typical values.The results showed that,according to the vegetation type,coniferous forest(C)had the best ecological benefit,while turf(L)had the worst ecological benefit;According to the vertical structure,the shrub structure had the best ecological benefit,while the grass structure was the worst.The results provide basic data for the study of soil microorganism and air microorganism in green space,and have important theoretical and practical significance for the optimization and improvement of urban green space plant allocation and green space structure.