不同盐度滨海盐渍土壤N2O排放特征OA北大核心CSTPCD

[Objectives]Coastal saline soils,as potential arable land reserves,harbor significant productive capacities.A win-win scenario for business and environment can be achieved by scientifically enhancing and employing saline soils while taking greenhouse gas emissions into account.We examined the N2O emission patterns from coastal saline soils at varying salinity levels in order to lay a scientific foundation for later efforts in salinity regulation and mitigating the greenhouse effect.[Methods]Natural coastal saline soils with varying salinity gradients were collected for the laboratory incubation experiment.The soil salinity levels were measured as 0.96,2.57,4.04 and 15.23 mS·cm-1,respectively labeled as Y1,Y2,Y3 and Y4.Gas chromatography was employed to monitor the emission characteristics of N2O from coastal saline soils at different salinity levels.[Results]Variable soil salinity levels resulted in dramatically variable N2O emissions.Soil N2O emissions decreased as salinity contents increased within the salinity range of 0.96 to 4.04 mS·cm-1.N2O production was again enhanced when the salinity contents reached 15.23 mS·cm-1.The emissions(2 598.94μg·kg-1)were second only to those recorded in soils with a moderate salinity level(5 384.17 μg·kg-1).The survival of soil microorganisms was stressed by the rise in salt.Salinity disturbances were more likely to affect ammonia-oxidizing bacteria(AOB)than ammonia-oxidizing archaea(AOA).AO A remained comparatively more abundant in soils that were either strongly or moderately salinized(Y1,Y2,Y3).On the other hand,the relative abundances of AOA and AOB decreased in heavily salinized soil(Y4),which hindered the nitrification process.Additionally,the cumulative N2O emission demonstrated a strong positive association with the potential denitrification rate(PDR)under the effect of the salinity gradient.One of the primary elements influencing denitrification was the amount of organic material present.Because microorganisms might directly use dissolved organic carbon(DOC),they had the ability to manage its turnover in soil.The abundance of the nosZ gene dramatically decreased as the salt content kept rising and the soil type was identified as saline.The nitrogen in the saline soil of Y4 eventually discharged in the form of N2O due to the inability to complete the N2O reduction process.[Conclusions]In coastal saline soils,the salinity gradient affected the nitrification and denitrification processes,which both significantly contributed to the transformation of soil nitrogen and produced distinct N2O emissions.The rising salinity contents lowered the rates of nitrification and denitrification,which decreased N2O emission in the range of 0.96-4.04 mS·cm-1 for EC25∶1.N2O emissions from nitrification processes(heterotrophic denitrification and nitrifier denitrification)became the main source of N2O emissions in saline soils,but nitrification production declined as the salt classification exceeded salty soil.