Climatic Significance of Surface Soil Organic Carbon Isotopes in the Monsoon Region of China

Objective Organic carbon isotope (δ¹³C_org) is an essential proxy indicator for paleoclimate reconstruction. To Clarify their climatic significance could provide an important basis for paleoclimate reconstruction.

Method The monsoon region of China was selected as the research area. Based on the existing 343 data sites, an additional 226 surface soil sample sites from Northeast China were added, resulting in a total of 569 data sites for analysis of surface soil δ¹³C_org. The study area was geographically divided according to the climate change gradient to investigate the correlation between δ¹³C_org and mean annual temperature (MAT) and mean annual precipitation (MAP) at different spatial scales and in different geographical regions.

Result The relationship between δ¹³C_org and MAT revealed a positive correlation at the overall spatial scale of the monsoon region. However, spatial heterogeneity existed in the correlation within different geographical regions (northern monsoon marginal and core zones, southern China, and Tibetan Plateau monsoon marginal and core zones). In the northern monsoon marginal and core zones, δ¹³C_org demonstrated a positive correlation with MAT, with temperature variations in the northern monsoon core zone exerting a more pronounced influence on δ¹³C_org. In the southern region, δ¹³C_org was negatively correlated with MAT. In the Tibetan Plateau region (including its monsoon marginal and core zones), δ¹³C_org showed no significant correlation with MAT. The relationship between δ¹³C_org and MAP revealed a positive correlation on an overall spatial scale. However, within distinct geographical regions, no significant correlation between δ¹³C_org and MAP was observed.

Conclusion Compared with the precipitation, the temperature representation of surface soil δ¹³C_org might be more significant. The climatic environmental controlled factors of surface soil δ¹³C_org varied across different spatial scales and geographical regions. During the subsequent paleoclimate reconstruction, it was necessary to combine regional modern process studies to improve the accuracy of environmental interpretation of the δ¹³C_org indicator.