Abstract:

Soil organic carbon isotopes (δ¹³C_org) can reflect the isotopic composition of growing vegetation and thus further reflect the vegetation type and the related climate. Previous studies have demonstrated that there are significant differences in the relationship between δ¹³C_org and climate factors in different regions. Therefore, it is essential to analyze the correlation between soil δ¹³C_org and climate factors in different regions for paleoclimate reconstruction. In our research, two transects of the Pamir Plateau and Qira County, located in the core of the arid region of Central Asia, are selected to analyze the carbon isotopic composition of surface soil and its relationship with climate factors to provide a scientific basis for paleoclimate reconstruction. In this paper, we first obtained 50 topsoil sediment samples and analyzed their organic carbon isotopic composition characteristics. Second, the relationship between soil organic carbon isotopes and climate factors was analyzed in detail. Finally, its potential driving mechanism was preliminarily explored. The results show that there are obvious differences in the relationship between surface soil δ¹³C_org and climate factors in the Pamir Plateau and Qira County: In terms of temperature, the Pamir region is positively correlated with annual average temperature (r=0.594, P<0.01), warm season temperature (r=0.593, P<0.01), and cold season temperature (r=0.598, P<0.01); the Qira County is negatively correlated with annual average temperature (r=−0.675, P<0.01), warm season temperature (r=−0.684, P<0.01), and cold season temperature (r=−0.646, P<0.01). In terms of precipitation, the correlation between the Pamir region and precipitation is insignificant; the Qira County has a weak negative correlation with the average annual precipitation (r=−0.485, P<0.05), a weak positive correlation with the warm season precipitation (r=0.483, P<0.05), and a significant negative correlation with the cold season precipitation (r=−0.632, P<0.01). Further mechanism analysis shows that the change in surface soil δ¹³C_org in the two regions is primarily controlled by temperature, but the correlation between surface soil δ¹³C_org and temperature is different due to the influence of glacier meltwater and the difference in vegetation types in the two regions. The correlation between surface soil δ¹³C_org and precipitation is insignificant due to glacial meltwater and very little precipitation. Our research shows that when reconstructing paleoclimate using organic carbon isotopes, more attention should be paid to the regional differences in the relationship between organic carbon isotopes and climate factors.

Key words: surface soil δ¹³C_org, temperature, precipitation, correlation analysis, arid area