[Spatial-temporal Evolution and Driving Force Analysis of FVC in the Arid Region of Northwest China]

The arid region of northwest China is one of the most sensitive areas in response to global change. Quantitative analysis of vegetation cover and its driving forces is crucial for protecting fragile ecosystems in the Northwest Arid Zone (NWAZ) and supporting high-quality economic and social development in the oasis. In this study, we investigated the spatial and temporal changes of the data of vegetation cover (FVC) in different subzones of the region by using the Sen's and Mann-Kendall tests with FVC and drivers from 2000 to 2022. Additionally, the stability of spatial and temporal changes of FVC and future development trends of FVC were analyzed using the coefficient of variation (CV) and the Hurst index method. The results showed that: ① Spatially, NWAZ showed a spatial pattern of "the north was larger than the south, the north-west was better than the south-east, and the mountainous areas were higher than the basins, " with the northern foothills of the Tianshan Mountains as the largest area of the FVC and the Tuha Basin as the smallest area. Temporally, the multi-year average of the FVC was 0.19, and the increase in FVC during the period of 23 years was 23.92%. ② Among the different subregions, the FVC improved significantly in the Alashan Plateau, Kunlun Mountains, and the east-central part of the Hexi Corridor and showed a decreasing trend in the northern part of the Hexi Corridor and the eastern part of the southern foothills of the Tianshan Mountains, etc. Overall, 67% of the regions showed an increasing trend in FVC. ③ The CV coefficient of the FVC in the NWAZ was relatively stable, with 66.7% of its area remaining stable. In addition, the mean value of the Hurst index was 0.58, with 81% of the area being greater than 0.5, demonstrating overall positive and continuous development characteristics. ④ Over the 23-year period, land use had the strongest explanatory power among factors influencing FVC in the arid region of northwest China, whereas nighttime lighting had the smallest explanatory power in factor probes. In interaction probes, topography and land use had the largest mutual driving effect, while topography and nighttime lighting had the smallest impacts. Moreover, spatial heterogeneity was significant in different subzones and years, demonstrating varying degrees of influence. The study revealed the spatial and temporal evolution of FVC and the driving mechanisms of its different factors, providing a scientific basis for ecological environmental protection and the sustainable development of oasis agriculture.