Spatial variation of surface soil color in the eastern Tibetan Plateau and its environmental significance

The color characteristics and spatial variation of surface soil in the eastern Tibetan Plateau (ETP) are important for understanding the relationship between soil color and modern climate factors and for reconstructing the Quaternary paleoclimatic environment. We analyzed in detail the spatial variation of surface soil color and its environmental significance. Results show that the spatial variation of surface soil color in the ETP is obvious. The soil brightness decreases first and then increases with latitude increase, and the redness and yellowness decrease with the latitude increase. In addition, the change in yellowness shows a parabolic curve from increase to decrease with longitude increase, and redness decreases with longitude increase. Both redness and yellowness decrease first and then slightly increase with altitude increase. The redness/yellowness ratio does not change significantly with latitude, but decreases with longitude increase, and increases with altitude. The spatial variation of soil color is resulted from the hydrothermal variation in local complicated arid semi-humid environment. In the study region of plateau, brightness decreases with precipitation increase within a certain precipitation range and is sensitive to precipitation. Redness and yellowness are sensitive to large-scale temperature changes. However, the response of redness to temperature is complex in a cold environment, which is related to precipitation. The redness/yellowness ratio indicates mainly the formations of hematite and goethite under special climate conditions, and the ratio is more sensitive to precipitation in arid and semi-humid areas than to temperature. The spatial variation in the color of surface soil reflects the spatial variation of regional climate factors under modern atmospheric circulation to a certain extent. However, due to the complexity of terrain and climate in the ETP, the relationship between color parameters and climate is complex. One should be careful in rebuilding the paleoenvironmental history from loess in the ETP.