Soil Carbon Distribution And Stable Isotope Variation In The Southern Margin Of Junggar Basin Desert

To explore carbon source and transformation in soil-vegetation ecosystem is an important part of the study on the carbon cycle in arid region,which can contribute to its rational management and protection as reference.In this paper,the southern margin of Junggar Basin Desert in Middle Asia was selected as the resear ch field.Three belt transects were set according to the distance from the desert to the oasis respectively in edge,middle part and hinterland of the desert,and soil profile sample with depth of 200 cm were collected.Then soil organic carbon?SOC?and soil inorganic carbon?SIC?content and the distribution characteristic of stable carbon isotope were studied.Additionally,the relationship between the changes in soil carbon and the distance to oasis was discussed.Results indicated that SOC content reduced as the soil depth increased.Influenced by the distance to oasis,the SOC content for the edge,middle part and hinterland of the desert were presented in descending order.With the changes of soil depth,SOC ?¹³C value ranged from-25.199‰ to-17.418‰,increased first and then declined,and the gathering occurred when it was 80 cm deep.Hence,C3 plants played a dominant role in the ground vegetation of southern margin of Junggar Basin Desert.However,there was succession process in the edge of oasis from dominated by C3 plants to dominated by C4 plants.On the contrary,due to the effect of carbonate illuviation,in 80% of the sampling points,SIC content increased first and then decreased as the soil depth increased.It gathered in the depth of 80 cm.SIC ?¹³C value reduced and then increased with soil depth increased.It gathered at the bottom mainly due to the impact of original carbonate content and soil carbon dioxide.Soil C isotope changes have certain significance for vegetation succession and soil strength.The spatial distribution of carbon and its isotopes in the study area was studied by using Kriging interpolation to analyze the depth of organic carbon isotopes and inorganic carbon isotopes in the study area.The results show that the spatial distribution of soil organic carbon ?¹³C in 0 20 cm is generally southwest,and the southwest is low,and the change is relatively moderate.The proportion of the area corresponding to the lower value of the ?¹³C value of the organic carbon increases gradually,that is,the percentage of the area occupied by the lower value of the organic carbon ?¹³C is gradually increased.The ?¹³C values of the organic carbon in the middle of the range of 30 80 cm change greatly,and the maximum center of gravity is also migrating continuously.From the beginning of the southwest to the northwest region,and then migrated to the southeast region,the upper and lower layers vary greatly.The distribution is relatively unstable.The ?¹³C value of organic carbon in 80 200 cm is the largest,and the ?¹³C content of organic carbon is high in the northeast and southeast regions.At the same time,with the deepening of the depth,the maximum value is approaching to the middle and spreading to the west.The low value area is relatively Big.The results show that the spatial distribution of 0 20 cm is similar to that of surface space.The ?¹³C content of inorganic carbon is generally high in the west and low in the east,but the mean value is larger than that of the surface,and the change is relatively moderate.The proportion of the area corresponding to the lower value is gradually increased That is,the percentage of the area occupied by the lower value of the ?¹³C value of the inorganic carbon is gradually increased.30 80 cm within the range of inorganic carbon ?¹³C value changes greatly,the maximum center of gravity is also constantly moving,and the area continues to increase,low-value areas continue to spread to the southeast corner,the area becomes smaller and smaller,only the total area of 5 %,And the distribution trend of organic carbon ?¹³C value is opposite.80 200 cm inorganic carbon ?¹³C value of the change is small,the content was generally high in the southwest.