[Spatiotemporal Dynamics of NDVI in the Tarim River Mainstream and Its Influencing Factors]

Identifying the temporal and spatial variations of vegetation cover and their driving factors in the mainstream of the Tarim River is crucial for protecting the ecosystem stability in the basin. Based on the normalized difference vegetation index （NDVI）， climate， topography， and anthropogenic factors of the mainstream of the Tarim River from 2000 to 2020， the spatiotemporal dynamic variation characteristics of NDVI in the mainstream of the river during 2000 and 2020 were analyzed by Theil-Sen Median slope estimation， Mann-Kendall trend significance test， Hurst index， and geographic detector， and the influencing factors of NDVI were evaluated. The results of the study follow： ① During 2000 to 2020， the NDVI in the mainstream of the Tarim River showed a fluctuating upward trend， with an increase rate of 0.001 2 per year， mainly dominated by low vegetation cover， accounting for 59.4% of the area. The spatial distribution of NDVI was obvious， with 44.9% of the area showing an increasing trend. ② The Hurst index analysis indicated that 64% of the NDVI area showed an improvement trend， while 36% of the area showed a degradation trend. ③ The influence detection showed that elevation was the main driving factor， with a q value of 0.421 9， and that the interaction between air temperature and elevation was the most significant effect， with a q value of 0.532. The ecological detection showed that there was a continuous significant difference between precipitation and air temperature on the change of NDVI， while there was no significant difference between slope aspect and night light. ④ The spatial differentiation of NDVI in the upper reaches of the river is primarily caused by the combined effects of climatic factors and topographic factors， but in the middle reaches， there is a gradual transition to human factors. Human factors are the dominant factors in the downstream region. Therefore， the NDVI in the mainstream of the Tarim River has shown an improvement trend through the past 20 years， and the NDVI situation in the region will depend more substantially on the balance of hydrothermal conditions in the future.