Late Quaternary environmental changes and organic carbon density in the Hunshandake Sandy Land, eastern Inner Mongolia, China

Knowledge about changes of regional carbon density during late Quaternary is of great significance for understanding regional and global carbon cycles. Taking the Hunshandake Sandy Land, located in eastern Inner Mongolia of China as an example, this paper aims to reconstruct Late Quaternary environmental changes, and then to discuss the fluctuations of organic carbon density and storage in the desert environment of northern China. The study area with a mean annual precipitation ca. 300 mm is characterized by the occurrence of fixed and semi-fixed sand dunes reaching a maximal height of 30 m. The research methods included field observations, examinations of grain sizes, as well as carbon and calcium carbonate contents of the sediment samples. The chronology is based on Optically Stimulated Luminescence (OSL) dating and radiocarbon analyses. This work reveals that the organic carbon density in the surface layer of the Hunshandake Sandy Land changed between at least 2500 g/m2 during the Holocene Climatic Optimum and 1500 g/m2 when aeolian processes dominate. The dune construction was restricted by periglacial processes during the Last Glacial Maximum (LGM). The Holocene Climatic Optimum, indicated by extensive formation of kastanozem soils, occurred between 5 ka and 3 ka in the study area. Although desertification might cause a 40% loss of total organic carbon storage within several dozen of years in the study area, a considerable amount of this carbon was re-deposited in the regions of downwind directions.