## 3 Results and Discussion
### Spatial Distribution Characteristics of Vegetation Cover  
It can be seen from Figures 5 and 6 that the spatial distribution of FVC in the research area is significantly different in different years, except that three reservoirs and two rivers are not defined. It can be roughly divided into three stages: the first stage is from 1990 to 2000, and the distribution of vegetation coverage shows a polarization between extremely high vegetation coverage and extremely short vegetation coverage. The extremely short vegetation coverage area is the unrealiomed bare land in the desert, with the average proportion dropping from 52.4% to 47.7%; the proportions of medium vegetation coverage area and high vegetation coverage area increased, up from 6.9% to 11.8% and 9.5% to 12.3%, respectively. The second stage is from 2000 to 2010, and compared with the previous stage, the vegetation coverage area significantly increased. During this period, the desert bare land was reclaimed into cultivated land, forest land, etc., with a relatively uniform spatial distribution, and the proportion of bare land decreased from 47.7% to 37.2%; vegetation coverage increased, in which the proportion of medium coverage area and high coverage area increased to 12.9% and 19.2%, respectively. The third stage is from 2010 to 2020, and the proportion of desert bare land gradually decreased and stabilized at about 27%. The vegetation coverage area gradually tended to be stable after increasing, and the proportion of medium and high vegetation coverage areas increased to 21.4% and 24.8%, respectively. There is little difference in the proportion of medium and high vegetation coverage areas in this decade.  
Figure 4: Spatial distribution of each seasonal vegetation coverage in 2020.  
In the recent 30 years, the vegetation area in Alar City has been increasing continuously, most of the desert areas have been reclaimed, the high vegetation coverage area has increased from 9.5% to 24.8% and the low vegetation coverage area (desert bare land, etc.) has decreased from 52.4% to 26.8%. The proportion of high vegetation coverage areas is uniformly distributed in Alar City. Most of the high vegetation coverage areas are near the reservoirs, Tarim River and other areas with plenty of water. The proportion of medium vegetation coverage areas is relatively scattered. The short vegetation coverage area accounts for the lowest proportion and is mostly distributed in the desert around the third, eleventh and twelfth regiments (special administrative division of the plan with the same administrative level as a town). In general, from 1990 to 2020, the overall trend  
Figure 5: Spatial distribution of different levels of vegetation coverage in different stages.  
Figure 6: Hierarchical distribution of the changing trend of vegetation coverage. SD: Significant degradation; BS: Basically stable; SE: Significant enhancement.  
of vegetation coverage in the Alar Reclamation area was good, and the desertification control effect was significant, which led to the increase in cultivated land and forest land. The area of forest land in the second, eighth, tenth and eleventh regiments increased, and the increase in cultivated land was mainly distributed in the ninth, eleventh, twelfth and thirteenth regiments.  
In general, vegetation cover in desert oasis areas was dominated by an increase in cover during the period 1990-2020, and there were more significant differences in the spatial distribution of vegetation cover changes.