Study area and datasets

2.1 Study area

Tuha Basin is the abbreviation of Turpan and Hami Basin and located in eastern Xinjiang of China (86⁰44′55″-96⁰25′0″E, 40⁰49′13″-45⁰3′21″N, Figure 1), which comprises two districts (Gaochang and Yizhou) and four counties (Tuokexun, Shanshan, Balikun, and Yiwu). With the average elevation of 800 m and elevation drop beyond 5000 m, Tuha Basin shows high mountain in the north and low basin in the south.
Tuha Basin has uneven distribution of precipitation and temperature. Rainfall occurs primarily in the mountain areas between April and September annually. Annual precipitation is usually less than 20 mm, while evaporation can reach 3000 mm, causing typical arid climate, with the water resource mostly relying on the snow meltwater from the mountains. The annual average temperature is around 15 ⁰C. The maximum temperature exceeds 50⁰C in plain areas, whereas in the mountain areas, it only reaches 27 ⁰C.
In this study, we categorized oasis into natural and artificial oasis according to the oasis features and function (Guo et al. , 2016; Wang et al. , 2021). Natural oasis was defined as the basic ecological environment, including forest, shrubland, grassland and waterbody. Artificial oasis is formed by the combination of natural disturbances and human interventions, and predominant by cropland and built-up in Tuha Basin. Other land types (bare land, permanent ice and snow) were classified into non-oasis type. Generally, oases are situated in the plain area of Tuha Basin, with the elevation range of –50 to 300 m. There is a small percentage of oases embedded in river basins formed by the meltwater from snow mountains.