The Effects Of Exogenous Decomposing Microorganisms On Soil Microbial Activity And Community Structure

The decomposition of organic matter is the important process to keep the soil fertility level of soils.Soil microbes are the most important decomposer in the soil ecosystem.Hereby,it plays a major role on soil-fertility formation.Exogenous decomposing microorganisms are often used to increase the decomposition of the fresh organic matter in soils,which leads to an increase of soil fertility.However,the effect of exogenous decomposing microorganisms on the organic matter in different soils is inconsistent.Red soil is distributed in the middle subtropics,in Southern China.Mollisol is distributed in the cool temperature zone,in Northern China.Thus,the difference of the level of soil fertility between the two soils above is very big.In this study,three kind of microbes,it is to say Paenibacillus pabuli(P),Streptomyces violaceorubidus(S)and Trichoderma aureoviride(T),were selected.For the experiments,in addition to the single microbe strains(P,S and T),the microbes were merged,resulting in combinations of two(PT,PS and ST),and three(PST)decomposing microorganisms(seven microbial agents in total).Moreover,there were three concentrations in every microbial agents.These microbial agents above were then added to two soils,which were the red soil and Mollisol separately.The red soil was sampled from the Jiangxi Province,in Southern China,while Mollisol was sampled from the Heilongjiang Province,in Northern China.Additionally,a control treatment,using sterile peat,was added to the experimental design.The experiment was conducted to study the effects of species' combination and inculation concentration of exogenous decomposing microorganisms on soil microbial community structure and metabolic activity.Hereby,the investigation aims at providing direct data support for the study of the effect of decomposing microorganisms on the decomposition of organic matter on different soil types.The main research results were as follows:1.Treatments adding single microbe strains(P,S and T)affected the logarithmic growth of microbes in red soil in the short term,and increased the peak of the respiration rate by 4.2%~118.7%.Treatment adding the combination of two exogenous decomposing microoganisms(PT)affected the logarithmic growth of microbes in Mollisol in the short term,and increased the peak of the respiration rate by 4.2%~118.7%.Additionally,with an increasing number of species of decomposing microorganisms,it took more time for microbes in red soil to enter the latent phase.However,there was no relation between the onset time of the latent phase for the microbes in Mollisol and the number of species of decomposing microorganisms.Moreover,the addition of single inoculant P and two strain PT increased the total metabolic capacity of microorganisms in Mollisol.The total metabolic capacity of microorganisms in red soil was enhanced only after adding the combinations of two(PS and ST),and three exogenous decomposing microorganisms(PST)in high concentration.2.The inoculation's concentration and species' combination of exogenous decomposing microorganisms exert a tremendous influence on the active microbial biomass in the red soil and Mollisol.Compared with the control,the active microbial biomass in red soil significantly increased under S,T and PT.The PLFAs content in Mollisol significantly decreased under S,T,PT and PS.The peak value of microbial biomass carbon in red soil was significantly increased by 58.8%-94.2% under T?PT and ST.The peak value of microbial biomass carbon in Mollisol significantly increased by 24.3%-43.0% under PST compared to the control.The peak value of microbial biomass nitrogen in Mollisol increased significantly with the increase of the concentration of exogenous fungal.3.There was no significant correlation between the inoculation concentration of exogenous microorganisms and the change of soil microbial community structure,but the microbial community in two soils significantly changed by the species' combination of exogenous decomposing microorganisms.The change in red soil microbial community structure varies with the treatments,among which the single microbe strains(P,S and T)was the smallest,while the combinations of three microorganisms(PST)was the biggest,compared to the control.The results showed the effect of the complex strains on the microbial community structure in red soil was stronger than that of the single microbe strains.The change in Mollisol microbial community structure varies with the treatments,among which the single microbe strains(P,S)and the combinations of three microorganisms(PST)was the smallest,compared to the control,while the single microbe strains(T)was the biggest,compared to the control.The study did not account for a relation between the variation of microbial community structure in Mollisol and the number of species of decomposing microorganisms.