Process Of Soil Organic Carbon Response To Climate Change In The Arid Area Of Saline Lake Surrounding

the background of global climate warming,the characteristics of greenhouse gas emissions has become one of the hotspots under global climate change.Effect of the land cover types to the carbon cycle of ecosystem.The land cover types have important influence on the process of soil organic carbon（SOC）,salt lake wetland as a special ecosystem in arid areas which different types of SOC process has a certain particularity to climate change.And regional ecosystem carbon sinks function evaluation has very important significance.The surrounding land cover types of xinjiang balikun salt lake include halophyte bush vegetation（HV）,saline grassland（SG）,carex wetland（CW）,farmland（FL）,dry lake（DL）.This study showed that the SOC,soil organic carbon density（SOCD）and soil CO₂ emission were analysed in the five land in Balikun Saline Lake in Xinjiang,China.In addition,this article also discusses soil CO₂emission response to climate change in the future（mainly including temperature,moisture and salt）.The main results are as follows:（1）The contents of SOC and SOCD showed that were different in five land cover types.The SOC content of SG,CW and FL treatments are the largest in 0-5cm soil layer,which decreases with the increase of soil thickness.The content of SOC was significantly different among different soil layers.SG,CW and FL treatments had the largest SOC content in 0-5cm soil layer,which decreased with the increase of soil depth.Meanwhile,the content of SOC was the largest in the 5-10cm soil layer for DL and HV treatments.There is a significant negative correlation between SOC and soil bulk density.Different land cover types of SOC was decrease with the increase of soil depth in CW,SG and FL.The SOCD continues to decrease,while DL and HV appeared with the increase of soil depth showed a decreasing trend after the first increase.Therefore,it is showed that the land cover types has the trend of soil organic layer thickening,which is beneficial to the increase of soil carbon reserves.Except for the DL,the change of soil CO₂emission rate showed the trend of single peak.There was a significant correlation between different months and soil CO₂ emissions（P<0.01）.In the relationship between soil CO₂ emission and all temperature indicators,SG and DL had the best correlation with the near surface temperature.（2）The warming conditions promote the soil CO₂ emission in 30℃incubator,the soil CO₂ emission was the highest in the wetland.Moreover,the land cover type under the conditions of soil CO₂ emission trends first declines gradually smooth.As a whole,higher temperature that can promote more the soil CO₂emission.From constant temperature 10℃to 30℃,SG and DL are in constant temperature 20℃,the highest soil CO₂ emission rate;the FL and CW is the highest at constant temperature 30℃,and the HV is relatively stable.（3）The variation law of soil CO₂ emissions in simulated precipitation treatment is not consistent.Compared with CK,16%treatment of soil CO₂ emissions are the highest,while 40%treatment was the lowest.The rainfall process significantly inhibit soil CO₂ emission meanwhile,decreases with the increase of rainfall soil CO₂ emission rate.In addition,humidity is the dominant factor for soil CO₂ emission.The soil water level significantly affects the soil CO₂ emission at the bottom of the DL.The soil CO₂ emission of 0 cm,-9 cm and-23 cm showed that a single peak curve,while the-34 cm and-45 cm water level showed a small change in soil CO₂ emission,which first decreased and then increased.There is a very significant（P<0.01）two function relationship between the soil CO₂emission rate and the water level at the bottom of the DL.Under different water level conditions,the difference of soil CO₂ emission from the DL of the Saline Lake was different.The soil CO₂ emission rate was the largest when the water level was-23cm at the bottom of the DL.The soil temperature sensitivity coefficient(Q₁₀)is significantly increased by the lowering of the water level.（4）The diurnal variation of soil CO₂ emission showed a single peak curve,with the peak value increased with amount of covered salt.The time of peak value showed in 15:00 O’clock under T₄ salt treatment（CK,no salt covering;T₁,T₂,T₃ and T₄,salt covering with 1,2,3 and 4 times amount of salt in soil）covering treatment,but 17:00 under other treatments.The flux of soil CO₂ emission was negative during 0:00 to 6:00.soil CO₂ emission showed a trend that first increase then decrease with incubation time after salt covering.Change of daily average soil respiration rate during incubation time and Q₁₀ value showed an increase trend with amount of covered salt,with daily average soil CO₂ emission rate under T₄treatment significantly higher than that under CK treatment.Our study suggested that it is not only temperature but also hydrothermal salt and its influence on Q₁₀value should be considered when study saline soil CO₂ emission under climate warming condition.