Effect Of Nitrogen Input On Nitrate Removal And Microbial Community Structure In Riparian Wetland

Nitrogen polluntion is one of the serious global enbironmental problems.Riparian wetlands that receive nitrogen input for a long time are important denitrification bioreactors.Due to the frequent fluctuation of hydrological conditions,the microoganisms involved in the soil nitrogen cycle have changed greatly.In this paper,the coupling effect of nitrogen input and water level fluctuation on the diversity of microorganisms involved in the soil nitrogen cycle was discussed,and reveals their effects on wetland soil nitrogen removal efficiency.This study collected undisturbed soil pillars of three typical communities(Calamagrostis angustifolia community?Carex pseudo-curaica community?Phragmites australis community)in QiXingHe National Nature Reserve in the summer of 2018.The independent design of undisturbed soil column simulated water level control device,to simulate nitrogen input and water level fluctuation of undisturbed soil microbial community in simulation experiment.Based on the results of 16S rRNA high-throughput sequencing,it explores the change of microbial diversity participating in the nitrogen cycle in a typical plant community in QiXingHe wetland.The results showed that:under the input of 30mg/L NO3-concentration,the nitrogen removal efficiency was largest in the Phragmites australis community;at 60mg/L NO3-concentration input,the removal efficency of nitrogen in the Carex pseudo-curaica community was the hightest.At the concentration of 30mg/L NO3-,when the water level fluctuated higher than the soil layer depth of 5cm,the relative abundance of bacteria in the Phragmites australis community was the largest,and the dominant bacteria was Thiobacillus.When the water level fluctuation was lower than the depth of the soil layer by 10cm,the relative abundance of bacteria in the Calamagrostis angustifolia community was the largest,and the dominant bacteria was Thiobacillus.When the water level fluctuation was lower than the depth of the soil layer by 20cm,the relative abundance of bacteria in the Carex pseudo-curaica community was the largest,and the dominant bacteria in this community was Pseudomonas.In three different communities,the relative abundance of the gunus is significantly different when the water level fluctuates.Under the addition of 60mg/L N03-concentration,when the level fluctuates 5cm above the depth of soil layer,the relative abundance of the bacteria in the Carex pseudo-curaica community is the largest,and the dominant bacteria was Pseudomonas;When the water level fluctuation was lower than the depth of the soil layer by 10cm,the relative abundance of the gunus Azospira was the largest in the Calamagrostis angustifolia community;When the water level fluctuation was lower than the depth of the soil layer by 20cm,the relative abundance bacteria in the Phragmites australis community was the highest,and the dominant bacteria in this commuity was Azospira.In different of water level fluctuation,the dominant genus in different communities changes significantly.In general,when the water level is lower than the depth of the soil layer,the relative abundance of the genus is greater.When compared with the concentration addition,it is found that the relative abundance of the bacterium genus is larger when the concentration is lower.The study enriches our understanding of the change rule of microorganisms in the case of exogenous nitrogen input in the QiXingHe River Nation Nature Reserve.