## 4 Conclusions  
Based on the Google Earth Engine cloud platform, taking the Alar Reclamation area as the research area, this paper calculated the time series of vegetation coverage in the research area for 30 years with the use of Landsat series image data from 1990 to 2020. In addition, analysis on the temporal and spatial pattern and variation trend was conducted from the aspects of Slope regression analysis, coefficient of variance, Hurst index, etc., and the role of human activities and climate factors in vegetation evolution was explored. It is expected to provide a scientific basis for ecological environment protection and the control of the desert oasis. The results indicate the following:  
1. From 1990 to 2020, desert control in the Alar Reclamation area achieved notable results, and the vegetation coverage showed a significant upward trend, with the R\({}^{2}\) of 0.89 and the annual growth rate of 3.8%/10a. The overall trend of FVC remained positive, but the variation rate and amplitude were different. The climate improved with the management of the environment and, due to its geographical location and other characteristics, the average annual amount of sunshine is currently sufficient and the vegetation cover is at its highest in the summer and lower in the spring due to the presence of extreme weather such as dust storms. The annual FVC mean in the research area shows a positive correlation trend of fluctuation change with a slow increase. 2. Based on the estimation of the Slope trend analysis, the vegetation coverage in the Alar Reclamation area in the recent 30 years has significantly improved, with the vegetation coverage improvement area accounting for 62.6% and the basically invariant area accounting for 19%. Among them, the area that has been improved and passed the significance testing accounts for 42.8% of the total area, showing a spatial distribution pattern of \"high vegetation coverage on both sides of the north and south of the Tarim River valley, low vegetation coverage in desert areas\". 3. The comprehensive analysis of the coefficient of variance and Hurst index shows that the overall variation trend and persistence of vegetation coverage in the whole research area are positively correlated with each other. In total, 89.52% of the regions with the coefficient of variance below 0.8 are in a relatively stable variation state, and 81.7% of the regions are characterized by medium and strong persistence in the Hurst index, concentrated on both sides of the Tarim River. 4. Human activities are the main driving factor for the improvement of vegetation coverage in the Alar Reclamation area; among the natural factors, precipitation is the most important factor affecting the vegetation growth in the research area, because the climate in the research area is mainly arid, with temperature having little influence. 5. There is a remote sensing image with long time span and multiresolution on the Google Earth Engine cloud platform, leading to a strong analytical and calculation ability with low time consumption. It is an effective tool to achieve monitoring of vegetation coverage at different scales. **Author Contributions:** Conceptualization, X.L. and Z.S. ; methodology, X.L. ; software, Z.S. ; validation, J.Y., J.L. and X.L. ; formal analysis, Z.S. ; investigation, X.L. ; resources, J.Y. ; data curation, Z.S. ; writing--original draft preparation, X.L. and Z.S. ; writing--review and editing, J.Y. ; visualization, X.L. ; supervision, J.Y. ; project administration, J.L. ; funding acquisition, J.L. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by Corps financial science and technology plan projects under Grants 2021 AB022. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The experimental data used to support the findings of this study are available from the corresponding author upon request.