Profile Distribution Characteristics Of Soil Inorganic Carbon And Carbon Sequestration Potential In Different Saline-alkali Degree Soil

In order to study the dynamic distribution characteristics of soil carbon in arid and semi-arid areas and investigate the carbon sequestration potential of pedogenic carbonates during the formation process,four saline-alkali soils with different conductivity in Hetao Irrigation District of Bayannur City,Inner Mongolia S₁?EC=5.64ms/cm??S₂?EC=10.86 ms/cm??S₃?EC=22.31 ms/cm??S₄?EC=31.13ms/cm?was selected as the research objects.Through the measurement of dissolved inorganic carbon content,inorganic carbon content,total inorganic carbon content,soil organic carbon content,and environmental factors?soil conductivity,pH?,the profile distribution characteristics and main influencing factors of SDIC,SIC,STIC,SOC and Soil carbon sequestration potential in saline-alkali soil were determined.And calculate the soil carbon sequestration potential of the soil with different saline-alkali degree by using the carbon stable isotope technique.The main results are as follows:?1?Distribution characteristics of soil dissolved inorganic carbon:The content of dissolved inorganic carbon in saline-alkali soil with different conductivity?S₁-S₄?varied from 0.0681 g·kg^-11 to 1.5482 g·kg^-1in the whole soil profile,decreased first and then increased with the depth of soil.The content of dissolved inorganic carbon in the upper layer?0¹00 cm?was less than the lower layer?100²00 cm?.The content of dissolved inorganic carbon in saline-alkali soil with different conductivity?S₁-S₄?decreased gradually with the increase of soil conductivity,which showed S₁>S₂>S₃>S₄.The average content of dissolved inorganic carbon in August was higher than that in May,and the maximum depth of each soil showed obvious downward movement.Through correlation analysis,SDIC was found to be negatively correlated with conductivity?EC??R²=0.7055,P>0.05?,but not significantly correlated with p H?R²=0.1168,P>0.05?,indicating that the greater the conductivity of saline-alkali soil,the stronger the leaching effect on dissolved inorganic carbon,and the more unfavorable to the accumulation of dissolved inorganic carbon.?2?Distribution characteristics of soil inorganic carbon:The results showed that the content of soil inorganic carbon in saline-alkali soil with different conductivity varied from 60.12 g·kg^-11 to 108.31 g·kg^-11 in the whole soil profile,decreased first and then increased with the depth of soil.The content of soil inorganic carbon in saline-alkali soil with different conductivity was the shallow layer accumulated to deep layer,and the maximum value appeared in 100¹30 cm soil layer.The content of soil inorganic carbon in saline-alkali area with different conductivity gradually decreased with the increase of soil conductivity,The average content of soil inorganic carbon in different saline-alkali degree soil in August was similar to that in May,and the depth of the maximum value was basically the same without obvious downward movement.The correlation analysis showed that the average content of soil inorganic carbon in soil decreased with the increase of EC,but the trend was not obvious?R²=0.8529,P<0.05?,and there was no significant correlation with pH?R²=0.3388,P>0.05?.?3?Distribution characteristics of soil total inorganic carbon:The content of total inorganic carbon in different saline-alkali degree soil varied from 60.25 g·kg^-11 to 108.47 g·kg^-11 in the whole soil profile,decreased first and then increased with the deepening of soil depth.The content of total inorganic carbon in shallow layer accumulated to deep layer,and the maximum value appeared in 100¹30 cm soil layer.The change rule of total inorganic carbon content of soil with different conductivity was the higher the conductivity,the smaller the total inorganic carbon content of soil.The content of total inorganic carbon in different saline-alkali degree soils was mainly soil inorganic carbon,and the average content of total inorganic carbon in May and August was similar.The correlation analysis showed that the total inorganic carbon content of soil decreased with the increase of EC,showing a significant negative correlation?R²=0.8578,P<0.05?,and increased with the increase of pH,but no significant correlation?R²=0.3386,P>0.05?.?4?Distribution characteristics of soil organic carbon:The SOC content of saline-alkali soil with different conductivity was measured at different depths of 0²00 cm soil profile.The results showed that the organic carbon content of saline-alkali soil with different conductivity varied from 0.9359 g·kg^-11 to 8.8381 g·kg^-11 in the whole soil profile was mainly distributed in the surface layer of 0³0 cm,and the content of0¹0 cm soil layer was the highest.With the deepening of soil depth,the organic carbon content gradually decreased.The main reason is that the surface soil is rich in nutrients and biomass.The content of organic carbon in saline-alkali soil with different conductivity was S₁>S₂>S₃>S₄,that is,the smaller the conductivity,the more organic carbon in saline-alkali soil.With the increase of conductivity,the content of organic carbon decreased gradually.The correlation analysis showed that there was a negative correlation between SOC and conductivity?EC??R²=0.4807,P>0.05?,but no significant correlation with p H?R²=0.1571,P>0.05?.Therefore,the conductivity of soil has a significant effect on the distribution and accumulation of organic carbon in saline-alkali soil.?5?Distribution characteristics of soil carbon sequestration potential:By measuring the carbon dioxide?¹³C values and soil carbonate?¹³C values at different levels of saline-alkali soil with different conductivity and using the isotope mass balance equation of pedogenic carbonates accumulation,the carbon sequestration potential of each soil layer in saline-alkali soil with different conductivity was calculated.The results showed that the distribution of soil carbon sequestration potential varied from 0.0200 g to 1.868 g in the whole soil profile and gradually increased with the deepening of soil depth,and the carbon sequestration potential of deep soil was greater than that of upper soil.The potential of carbon sequestration in saline-alkali soil with different conductivity decreased with the increase of soil conductivity,which was S₁>S₂>S₃>S₄.The correlation analysis showed that there was a negative correlation between soil carbon sequestration potential and conductivity?EC??R²=0.5879,P>0.05?,but no significant correlation with p H?R²=0.1450,P>0.05?.It can be concluded that soil electrical conductivity has a significant inhibitory effect on the process of carbon sequestration in saline-alkali soil.