Sites description and samples collection
The Taklimakan Desert is located in the northwest of China, specifically, in the southern region of Xinjiang province and the center of the Tarim Basin. The desert covers an area of 337,600 Km2 and 85% of the surface is occupied by active dunes (Yang et al., 2016). It is the largest desert in China, and the second-largest mobile desert in the world. The annual mean temperature ranges from 9.9 to 12.6 °C, annual precipitation ranges from 17.4 to 66.3 mm, and the potential evaporation range from 2,100 to 3,400 mm. It belongs to the extremely arid temperate continental climate (Zhu, 1964; Zhu et al., 1981). In this study, the free of vegetation and human activity areas were selected as sampling sites. A total of 48 sand samples along a north-south transect were collected with sterile sampling bags from 8 sites in the Taklimakan Desert in September 2018 (Fig. 1). At least three surface (0-5 cm, S) and subsurface (50 cm, Su) sand samples were separately collected at each sampling site. All the samples were transported to the laboratory within one week at a low temperature and then stored at -20°C. The detailed information of the samples is provided in Table S1.