Effects Of Intensive Management Of Mycorrhizal Fungi On Soil Microbial Community And Its Function In Phyllostachyspubescens Forest

In recent years,the ecological and environmental problems caused by the intensive management of Moso bamboo forest have attracted wide attention.Arbuscular mycorrhizal fungi are the bridge between plants,soil and microorganisms.The change of ecological environment has an important effect on the carbon and nitrogen cycling function of AM fungi.In this study,the fine roots and AM fungi were distinguished by in-situ microcosm systems with nylon sieves of different apertures.Thus,the four treatments were fine-root and mycelia in growth(RA),mycelia in-growth(AH),soil-only controls(NA),and an undisturbed soil collar(CK).Multiple analytical techniques such as gas chromatography,real-time fluorescence quantitative PCR and high-throughput sequencing were used to study the effect of intensive management on carbon and nitrogen cycling function of soil AM fungi and its response mechanism.The main results are as follows:(1)The different management intensity and compartment treatment had significant effects on soil physic-chemical factors,mainly manifested as that intensive management increased soil available nutrients,and available phosphorus and available potassium in the mycelial chambers(AH)significantly increased,but soil p H value in each compartment significantly decreased(P<0.05).After intensive management,the AOA gene abundance of soil was significantly increased in each chamber(P<0.05),while the AOB gene abundance showed a trend of decline and significantly decreased in the NA compartment that prohibited the passage of AM mycelia(P<0.01).Correlation analysis showed that p H value was the main control factor leading to the change in the abundance of ammonia-oxidizing microorganisms(P<0.05).Management intensity and compartment had significant effects on the number of ammonia-oxidizing microorganisms and Chao1 index(P<0.05),but they did not have significant effects on the community structure of ammonia-oxidizing microorganisms.(2)Different management intensities and compartmentalized treatments had different effects on soil enzyme activities and the results of NMDS analysis showed that there were significant differences in soil enzymatic activities between different compartmentalized treatments of intensively managed bamboo forests(P<0.01).Two-factor analysis of variance(anova)showed that compartment had a significant effect on AM fungus gene abundance(P<0.01).The structure of soil bacteria and fungus community was significantly different due to the different management intensity of bamboo forest(P<0.001).Correlation analysis showed that p H value,available potassium and?-glucosidase were the main environmental factors that caused the variation of bacterial community structure(P<0.05),while the variation of fungal community structure was significantly correlated with p H value,alkali-hydrolyzale nitrogen,available potassium and?-cellobiosidase(P<0.05).The soil CO₂ emission flux of bamboo forest showed a law of lower in winter and higher in summer,and was significantly correlated with the soil temperature at 5cm.After intensive management,the annual contribution rate of AM mycelia respiration increased significantly(P<0.05).In conclusion,this study suggests that intensive management changed the p H value of rhizosphere and hyphae soil,leading abundance changes of ammonia-oxidizing microorganism to impact the soil nitrogen,andchanges the biomass of AM fungi by changing the physical and chemical properties of soil in different compartments,which leads to the increase of the mycelia respiratory contribution rate of AM fungi and influences its carbon cycle function..