Nebkha development and its relationship to environmental change in the Alaxa Plateau, China

Extensive nebkha areas develop mainly under the control of aeolian processes, and their sediments record information on regional environmental changes during different periods. Such areas have developed on the dry riverbeds and deserted arable lands of China's Alaxa Plateau, Taklimakan, and Kumutage deserts. In this paper, we studied nebkhas that had developed in the Heicheng-Juyan region to determine their CaCO3 contents, particle size distributions, and creation dates. Extensive human activities have occurred in this region since at least in the late Tang Dynasty (618-907 AD). Although historical records show that most of the region's rivers dried up around 1372, surface water persisted in some areas until the early Qing Dynasty (1644-1911 AD). After the 1600s, extensive nebkhas began to develop due to drying of the region's rivers. The early stages of nebkha development were controlled by both the sediment supply and the regional wind regime, whereas late stages were controlled primarily by variations in wind activity. In the Alaxa Plateau, it took about 100 years for arable lands and riverbeds to evolve into gobi deserts, and during this time, several phases occurred with different levels of wind activity. The land degradation processes in this region are mainly controlled by surface water resources, and the impact of human activities such as reclamation on land degradation appear to have been overestimated in previous studies.