## 4 Discussion  
### Climate Change and Its Influence on the MODEI  
Ecosystems are sensitive to climate change, especially in arid areas [58]. Climate change can directly affect vegetation growth in the ecosystem through precipitation and temperature by affecting ground humidity, vegetation productivity, etc. [59]. Our results showed that the indicators of FVC, GPP, LAI, and WET had positive effects on the MODEI, while the LST indicator had a negative impact on the MODEI, results which were consistent with previous studies [29, 60].  
The annual precipitation in Fuyun County showed a fluctuating upward trend from 2008 to 2018 (Figures 9b and 10b). The annual precipitation in the study area increased from 185.01 mm in 2008 to 289.48 mm in 2018, with an average increase of 10.45 mm/year (Figures 9 and 10). The study carried out by [PERSON] et al. [61] showed that the vegetation productivity in arid and semi-arid areas was mainly controlled by precipitation. [PERSON] and [PERSON] [62] proved that meteoric precipitation was the main source of vegetation moisture in arid ecosystems in Central Asia, which can increase the soil water content, so the soil can provide more water for the vegetation to enhance its photosynthesis, thus improving the growth of the vegetation [63]. Therefore, the improvement of ecological conditions in the study area was mainly driven by the increase in precipitation, as the increase in precipitation directly increases humidity thus improves vegetation growth. The results showed that the decreased MODEI of summer pastures was mainly concentrated in the high-altitude mountainous area with abundant precipitation in the northernmost summer pastures (Figure 6b). However, when the precipitation exceeds the water level required for vegetation growth, the photosynthesis of vegetation will be inhibited due to the limited solar radiation and the increased relative humidity [35, 64].  
Figure 8: (**a**): Three-dimensional scatter plots illustrating the relationships among MODEI, FVC and GPP; (**b**): Three-dimensional scatter plots illustrating the relationships among MODEI, LST and LAI.  
Previous studies have shown that most vegetation in arid regions of Central Asia was more sensitive to changes in precipitation than to changes in temperature [33; 65]. The average temperature in the study area in 2008 and 2018 was 3.73 \({}^{\circ}\)C and 3.74 \({}^{\circ}\)C, respectively, with no noticeable trend of change (Figures 9a and 10a). The areas where  
Figure 10: Spatial distribution of average temperature and annual precipitation in 2018.  
Figure 9: Spatial distribution of average temperature and annual precipitation in 2008.  
the temperature dropped were mainly located in summer pastures, while spring and autumn pastures and winter pastures appeared to have a slight warming trend (Figure 11a). PCA and prediction model results showed that LST had a negative effect on the MODEL (Table 2). Therefore, in addition to the influence of precipitation change and human factors, the decreased temperature in summer pastures and the increased temperature in spring and autumn pastures and winter pastures may play a part in the increase in the MODEL in summer pastures and the reduction in the MODEL in spring and autumn pastures and winter pastures.