Effect Of Water Changes And Nitrogen Deposition On CH₄,CO₂ And N₂O Emission In Alpine Wetland Soil

Under the background of global warming,water changes and human activities will have a profound impact on greenhouse gas emissions in alpine wetlands.The study on the development of greenhouse gas emissions from alpine wetlands in arid regions responds to changes in soil moisture and simulated nitrogen deposition in wetlands,which not only enriches the content of carbon-nitrogen cycles in wetlands in China,but also provides reference for the development,protection and management of regional wetland resources.In order to investigate the laws of soil CO₂,CH4,and N2O emissions from alpine wetlands in the presence of water changes and nitrogen deposition,In this study,we studied the soil of alpine wetlands in Bayinbuluke,Xinjiang,through an indoor simulation control experiment,Under changes（100%,80%,60%,40%and 20%WFPS（water filling soil porosity））,nitrogen addition(N0(0 kg·hm^-2·a^-1),N10(10 kg·hm^-2·a^-1),N20(20kg·kg·hm^-2·a^-1),and N100(100 kg·hm^-2·a^-1))treatment of soil CO₂,CH₄,and N₂O in alpine wetlands in Bayinbuluke impact of emissions.The results showed that:（1）The addition of ammonium nitrate under dry-wet alternation promoted the CO₂ emission in the wetland soil,the average CO₂ discharge rate between the five WFPS treatments had extremely significant difference（P<0.01）.Ammonium nitrate addition inhibited the emission of CH4 in soil and showed the law of"nitrogen promotes carbon sink".In the N0 and N100 treatments,there was a significant difference in the average CH4 emission rate between 100 and 20%WFPS treatment（P<0.05）.The addition of ammonium nitrate in dry-wet alternate second cycle has the most obvious effects on the N2O emissions from wetland soils,the average N2O emission rates of 100,60,40,and 20%WFPS treated soils decreased with the decrease of soil WFPS.（2）The rate of CO₂ emission from wetland soils treated with urea alternately wet-dry was significantly higher than that without nitrogen treatment,soil CO₂ emissions increase with increasing soil moisture,there was a significant difference in the average rate of soil CO₂ emission between 80,60,40,and 20%WFPS（P<0.01）,the peak time of soil CO₂ emission in each cycle lags behind the addition of ammonium nitrate.Addition of urea treatment promotes soil CH4 emissions overall.In addition,the peak time of soil CH4 emission was significantly delayed compared with ammonium nitrate nitrogen addition.With the increase in the number of alternating wet and dry cycles,soil CH4 emissions gradually increased.The rate of N2O emission from the urea treated soil was lower than that from the N0 treatment,in the treatment of 100%and 80%WFPS,the N2O emission rate has a great influence on the soil,the law is consistent with the addition of ammonium nitrate and nitrogen.（3）The addition of ammonium nitrate initially stimulated CO₂ emissions from the soil under constant humidity conditions,with the prolonged constant humidity,soil CO₂ emission rate declines,after about 20 d tends to balance.Add ammonium nitrate differently at 100%WFPS,the impact on the rate of CH4 emission from soil is greatest,after 10 d of culture.they first increased and then decreased.The N2O emission from soils treated with ammonium nitrate was decreased with the decrease of WFPS,there was a significant difference in the average N2O emission rate between 100,80,and20%WFPS（P<0.01）.There was no significant difference in the average N2O emission rate between soils treated with 60 and40%WFPS（P>0.05）.（4）The addition of urea initially stimulated the soil CO₂ emissions under conditions of constant humidity,with the extension of the constant humidity process,the rate of soil CO₂ emission decreased.However,the time when the soil CO₂emission tends to equilibrate is about 5 d earlier than that of adding ammonium nitrate.There was a significant difference in the average CO₂ emission rate between the 80,60,40,and 20%WFPS treatments（P<0.05）.When WFPS is 100%under urea treatment,it has the greatest impact on soil CH4 emissions,after 10 days of cultivation,there was a rise and then a downward trend,after 10 days of cultivation,there was a rise and then a downward trend.The average discharge rate of soil CH4between 20-80%WFPS treatment was not significantly different（P>0.05）.Urea addition promotes the soil N2O emissions,when N20 and N100 were treated at 100%WFPS and N0 and N10 were treated at 80%WFPS,the soil N2O emission tended to fluctuate.However,the soils N2O emission trends in other WFPS treatments are similar.