Study On Soil Carbon Pool Transfer In Arid Oasis Based On Stable Carbon Isotope Technique

The soil carbon in arid regions is an important part of the global carbon pool.In the soil,through the soil organic carbon-soil CO₂-soil inorganic carbon microcirculation system,the transfer of soil organic carbon to soil inorganic carbon occurs,while the soil carbon pool is small.The changes can affect the global carbon balance,lead to global climate change,and then affect the carbon conversion and carbon cycle of terrestrial ecosystems.The purpose of this study was to measure soil organic carbon?SOC?and soil inorganic carbon?SIC?in 4 types of soils,ie,aeolian sandy land,irrigated desert soil,brown desert soil,and saline soil in the northern margin of the Tarim Basin.The correlation between the two was obtained.The stable carbon isotope technique was used to analyze and determine the SIC,SOC,soil CO₂?¹³C values,determine the proportion and content of occurring carbonates,and explore the sources and proportions of fixed CO₂ during its formation or recrystallization,in order to obtain the transfer of soil organic carbon to soil inorganic carbon,combined with Pearson correlation analysis and path analysis to obtain the impact of different physical and chemical factors on the amount of transfer.The purpose of the study was to explore the transfer patterns of soil organic carbon to inorganic carbon in the oasis of arid regions,and to provide some data foundations and theoretical support for further exploration of the terrestrial ecosystem carbon cycle.The main result were the following:?1?4 kinds of soil SOC and SIC content were significant differences in study area.SOC content of 4 soil profiles in aeolian sandy soil,irrigated desert soil,brown desert soil and saline soil were?2.41±0.15?g/kg,?4.50±0.31?g/kg,?4.06±0.38?g/kg,?3.69±0.10?g/kg,respectively.SIC content of 4 soil profiles were?99.46±4.33?g/kg,?225.90±3.09?g/kg,?150.74±2.86?g/kg,?147.22±1.57?g/kg,respectively;Pearson correlation analysis showed that there was a positive correlation between SOC and SIC in sandy soil,brown desert soil and irrigated desert soil,the irrigated desert the soil reached significant level,with the soil profile decreased gradually;saline soil was negative correlation,as the soil profile deepens,SOC decreased,SIC increased gradually.?2?There were significant differences in SIC and soil CO₂ of soil ¹³C values of the four soil in the study area.The mean values of SIC of ¹³C in aeolian sand soil,irrigation desert soil,brown desert soil and saline soil were?0.21±0.09?‰,?-0.32±0.06?‰,?-1.99±0.06?‰and?-1.12±0.12?‰respectively,indicated that the ratio and content of the organic carbonate were low in aeolian sand soil and irrigation desert soil,the saline soil and brown desert soil were higher.The mean value of SOC of ¹³C in the soil profile were?-23.88±0.27?‰,?-24.75±0.36?‰,?-24.63±0.52?‰and?-23.77±0.55?‰respectively,the average of CO₂ of ¹³C values in the soil profile were?-12.60±0.34?‰,?-18.54±0.29?‰,?-17.63±0.34?‰,and?-12.70±0.85?‰respectively.According to the two ends of the isotope,the proportion of atmospheric CO₂ in the sand soil and saline soil was high,followed by the brown desert soil,and the lowest was irrigation desert soil.?3?According to the isotope mass balance equation for quantitative analysis of aeolian sandy soil,irrigated desert soil,brown desert soil and saline soil of pedogenic carbonate ratio were 1.71%,5.21%,17.99%,39.18%respectively,content were 1.73g/kg,12.01 g/kg,26.35 g/kg,61.58 g/kg respectively;The aeolian sandy soil,irrigated desert soil,brown desert soil and saline soil in carbonate formation of fixed soil during CO₂ were 0.38 g/kg,2.64 g/kg,5.80 g/kg and 13.55 g/kg respectively by the isotope abundance method for pedogenic carbonate,the atmospheric CO₂ was fixed for an average were 0.26 g/kg,1.07 g/kg,2.29 g/kg,10.8 g/kg respectively,fixed soil respiration emission were 0.12 g/kg,1.58 g/kg,3.51 g/kg,3.27 g/kg respectively,indicating a high content fixed from the atmosphere of CO₂ in aeolian sandy soil and saline soil,while irrigated desert soil and brown desert soil fixation from soil respiration release of high CO₂ content.The soil respiration in aeolian sandy soil,irrigated desert soil,brown desert soil and saline soil SOC oxidation decomposition into CO₂ for the amount of 0.06 g/kg,0.79 g/kg,1.75 g/kg and 1.64 g/kg respectively,the transfer amount from SOC to SIC were between-2.61g/kg and 0.02g/kg of the whole soil,the average per kilogram of soil fixed 1.05g CO₂,that the oasis soil organic carbon in arid area with less.?4?The correlation between carbon transfer amounts and soil physicochemical factors in different types of soil indicated:In the aeolian sandy soil,there was a positive correlation between the amount of carbon transfer and the electrical conductivity,and the direct path coefficient and the decision coefficient of the electrical conductivity were the largest,being 0.42 and 0.40,respectively.It was the main decision factor and had a strong positive direct effect on the amount of transfer.In irrigated desert soils,the transfer amount had a positive correlation with SOC,and the SOC direct path coefficient and decision coefficient were the largest,which were 0.62 and 0.77,respectively,and were the main decision factors.In the brown desert soil,the carbon transfer amount was positively correlated with the SOC content,and the highest SOC decision coefficient was 0.41,which was the main decision factor.In saline soils,the relationship between the amount of transferred carbon and the soil physicochemical factors was not significant,and the maximum value of the pH value decision coefficient was 0.19,which was the main decision factor.