Effects Of Increasing Temperature On Soil Carbon And Nitrogen Transformation And Its Microbial Mechanisms In A Peatland Of The Great Hing'an Mountains

Northern peatlands considered as crucial carbon and nitrogen pool worldwide,yet their related carbon and nitrogen dynamics are highly sensitive to changes in climate.Carbon and nitrogen transformation in this region affected by climate warming directly or indirectly,thus forming feedback effect.Although predecessors had done a lot of research work on this,further and detailed study of climate warming effects on carbon and nitrogen content and transformation process in northern peatlands and their microbial mechanism still need to know.Here,we sampled peatlands soil columns in the Great Hing'an Mountains and studied the effect of temperature increasing variations on soil carbon and nitrogen transformation and its microbial mechanism by indoor simulation incubation.Main conclusions showed as follows.(1)Temperature increasing stimulated CO₂ and CH₄ emission rates and cumulated amount significantly among the whole depths(0-150 cm).It enhanced abundance of carbon and nitrogen cycle related microbes in active layer(0-40 cm).These findings suggested that warming promoted CO₂ emission through increased the microbial abundance.(2)Temperature sensitivities(Q₁₀)values of CO₂,CH₄ emission,and microbial abundance were CO₂(2.39),CH₄(55.49),bacteria(1.17),fungi(3.85),archaea(1.76),methanogens(1.68),methanogens(1.66),nir K-type denitrifying bacteria(2.53),nir S-type denitrifying bacteria(1.22),respectively.Sensitivity of CH₄ to temperature is much higher than that of CO₂,indicated that CH₄ release was more susceptible to temperature change.In addition,temperature sensitivity of soil microbe in active layer is stronger than transition layer and permafrost layer(40-150 cm).(3)Temperature increasing significantly promoted soil organic carbon(SOC)mineralization,increased available nitrogen content,and decreased invertase and urease activities in 0-10 and 10-20 cm depth.This showed that increase of temperature would change availability of soil nitrogen substrate.Glucose addition caused positive priming effect of SOC mineralization in the early stage of the incubation and turned into negative priming effect in the late of the incubation.The cumulative SOC mineralization amounts with glucose added at 15 ^oC is about the same level as that without glucose added at 5 ^oC.In the long run,exogenous carbon addition induced negative priming effect may decrease carbon losses in northern peatlands that exhibit warming-induced carbon decreases,thus partially buffering soil carbon content against change.The decomposition of plant litter and the increase of active carbon input from roots caused by climate warming can regulate carbon dynamics by changing MBC,DOC,NH₄⁺-N contents,?-glucosidase activity and fungal abundance.(4)The Q₁₀ value of soil organic carbon mineralization was significantly correlated with changes of soil DOC,NH₄⁺-N contents,enzyme activity,fungi:bacteria ratio caused by temperature increasing,and active carbon addition could significantly increase Q₁₀ value.The effect of temperature on SOC mineralization was influenced by the microbial abundance and carbon and nitrogen substrate availability.