Effects Of Increased Temperature On Soil Nitrogen Transformation From Alpine Peat Wetland And Its Microorganism Mechanism

The problem of global warming caused by the increase of atmospheric CO2 concentration in recent years is obvious.The response of microbes to global warming significantly affects the biogeochemical processes they drive.The research was carried by open top chamber(OTC)in Alpine peat wetland,using the open top chamber to realize multi field gradient increasing greenhouse warming.The response of soil nitrogen process to warming was investigated.High-throughput sequencing was used to detect nitrifying and denitrifying bacteria to reveal the influence mechanism.Through the field monitoring of a full growing season,the main results are shown:The climate in OTC tended to be warm and dry.Air temperature was elevated by 1.45,2.70 and 3.67?,and soil temperature was elevated by 0.72,1.01 and 1.46?.Increasing temperature also lead to soil water to decrease.The effect of increasing temperature on soil nitrogen transformation was influenced by group structure of nitrification bacteria and enzyme activity.Low temperature significantly increased the diversity of soil nitrifying bacteria,instead of denitrifying bacteria.The diversity reduced by 33%and 38%(nitrifying bacteria),24%and 12%(denitrifying bacteria)by medium and high level temperature increase.Meanwhile,in 6-8 months,medium temperature elevated soil microbial biomass concentration.In August,high temperature treatment significantly decreased soil microbial biomass carbon activity by 8%.The increase of temperature has a tendency to increase the activity of nitrate reductase in soil.Warming increased microbial activity which made the microbial growth accelerate.However,when the increase in temperature exceeded the adaptability of microorganism,the activity of microorganism was decreased.Soil moisture decreased the microbial growth and reproduction which decreased the activity due to water condition restriction.There was significant increase in inorganic nitrogen content in soil in 7-8 months.Low and medium warming significantly elevated soil N2O flux,but high temperature treatment made it significantly decrease by 23%.The rate of soil nitrification increased significantly in medium and low temperature treatment,but high temperature treatment reduced the promotion on nitrification rate.This indicated that there might be a certain optimum temperature and moisture in soil nitrogen transformation.The positive effect brought by warming is only in the appropriate temperature range.The high temperature makes the promotion effect of warming on nitrogen transformation process possibly be limited by water limitation.Combined with the actual warming trend in China and Qinghai Tibet Plateau,future climate warming will increase soil nitrifying microbial community species diversity,and is conducive to nitrification process and soil N2O flux.