Comparison Of Soil Microbial Diversity Of Different Plants And Rhizosphere In Dongtan Wetland

Chongming Dongtan Wetland is located on the east side of Chongming Island in Shanghai,at the mouth of the Yangtze River.At the same time,the wetland environment,as the most productive area on earth,is located in the transition zone between terrestrial and aquatic environments.Due to the action of aerobic and anaerobic microbial activities,the wetland environment has the ability to rapidly cycle nutrients and absorb the global greenhouse gas.The microorganisms present in the wetland environment play an important role in the decomposition of organic matter.In 2000,a large number of Spartina alterniflora invaded Chongming Dongtan Wetland Park,which seriously damaged the original ecological environment and had a negative impact on the ecosystem.Vegetation directly affects the microbial diversity in soil by affecting soil organic carbon and nitrogen content,sulfur content,soil moisture content,temperature,and pH,etc.,and soil microorganisms also affect the composition of surrounding soil,thereby changing the ecological environment of the soil.This further affects the ecological environment of the surrounding rivers.The structure of wetland soil microbial community is also closely related to the nutrient supply of plant roots.At the same time,previous studies have shown that the composition of soil microbial community structure varies significantly under different plant species.Therefore,exploring the microbial community diversity,physicochemical parameters and organic matter content changes in the rhizosphere and non-rhizosphere soils of invasive plants and primitive vegetation has important indicative significance for the improvement of the surrounding ecological environment in the future.In this study,9 stations were selected for sampling in the Dongtan wetland of Chongming Island,each station covered 3 parallel samples,a total of 48 samples of rhizosphere and non-rhizosphere soil were collected,and the following indicators were measured for all samples:total organic carbon（TOC）and total nitrogen（TN）content,carbon and nitrogen stable isotopes(δ¹³C,δ¹⁵N),particle size,water content,pH.One sampling point for each of the three plants was selected for microbial bacterial and fungal sequencing.The data obtained are mainly analyzed from the following three aspects:1.Differences between the physical and chemical properties of the underground rhizosphere soil and the surrounding non-rhizosphere soil of three different plants,Spartina alterniflora,S.2.The differences in microbial community structure between the underground rhizosphere soils of three different plants and their surrounding non-rhizosphere soils,in which the differences between bacteria and fungi were mainly explored.3.Combine the physical and chemical properties,organic matter and stable isotope indexes of three different plants with the microbial community structure to explore the differences between invasive plants and original vegetation.Through the analysis of the above three aspects,the following conclusions are drawn:1.The total organic carbon and nitrogen contents in the rhizosphere and non-rhizosphere soils of Spartina alterniflora and S.However,the nitrogen isotope(δ¹⁵N)content in the rhizosphere and non-rhizosphere soils of Phragmites reed at station 8 was significantly higher than that in the rhizosphere and non-rhizosphere soils of Spartina alterniflora（TOC:1.41%±0.64%vs.0.242%±0.132%;p<0.01 TN:0.145%±0.044%vs.0.034%±0.016%;p<0.01）.It contains special bacteria cyanobacteria,which have nitrogen-fixing effect.Previous studies have shown that the rhizosphere soil of reed contains a higher abundance of nitrogen-fixing bacteria（5.97‰±1.585‰vs.9.49‰±3.44‰;p<0.05）.Therefore,nitrogen-fixing bacteria resulted in higher nitrogen isotope(δ¹⁵N)content in the rhizosphere and non-rhizosphere soils of the reed plot.2.The nitrogen isotope(δ¹⁵N)of the rhizosphere soil and non-rhizosphere soil of Spartina alterniflora and Spartina alterniflora is similar,but the nitrogen isotope(δ¹⁵N)of the rhizosphere soil and non-rhizosphere soil of Reed is quite different.This shows that for the microbial community in the rhizosphere soil,the rhizosphere soil bacteria of Spartina alterniflora have stronger utilization of nitrogen isotopes in the soil,while the effect of the rhizosphere soil bacteria of Phragmites reed on the surrounding soil environment is weaker.3.The bacterial richness in the rhizosphere soil of reed is greater than that in the rhizosphere soil of Spartina alterniflora and S.alterniflora,while the richness of fungi in the rhizosphere and non-rhizosphere soils of S.alterniflora is lower than that in Spartina alterniflora and S（0.66±0.2%vs.3.65%±2.32%）.The relative abundance of bacteria unclassified＿g＿＿Thiobacillus in Spartina alterniflora is relatively high.This flora is a type of sulfur bacteria.Previous studies have confirmed that the adsorbed soluble s^2-in Spartina alterniflora can be rapidly oxidized to fixed in plants.SO₄^2-.This has a certain correlation with the relatively high relative abundance of sulfur bacteria in the rhizosphere and non-rhizosphere soils of Spartina alterniflora.4.The invasion of Spartina alterniflora resulted in the decrease of soil pH,which could be attributed to the following two reasons:first,there were acidic chemicals in the litter and root exudates of Spartina alterniflora,which led to the decrease of soil pH;Second,organic matter will provide more protons to the soil solution during the decomposition process,and Spartina alterniflora has higher primary productivity.Therefore,in the pH of soil samples at 9 points measured,the pH value of spartina alterniflora region is significantly lower than that of the other two plants region In addition to affecting the composition of bacterial population in soil,the change of soil pH value also affects the rhizosphere secretions of plants.To sum up,the interaction between soil pH value and plants needs further study...