## 4 Discussion  
The response of vegetation to climate factors is key to explaining the ecosystem dynamics and structure [8; 9; 11; 63]. Climate change has a different influence on the ecosystem indicators across different climate zones. Arid and semi-arid zones dominate the Xinjiang region, and therefore, water availability is the main climate factor for limiting vegetation growth [8; 11; 64]. Precipitation is positively correlated with the ecosystem indicators in more than 68% of the area due to the vulnerability of vegetation growth to water variation (Figure 11). The positive correlation between the climate factors and the ecosystem indicators is lower in the hyper-arid zone than in the arid zone. It is possible that soil moisture deficit during the growing season counteracts the benefits of precipitation and that moisture stress reduces the positive effect of the climate factors on the ecosystem indicators [65]. As the climate becomes wetter, the positive effect of precipitation on the ecosystem indicators diminishes due to increased precipitation (Figures 9 and 11). The negative effect of precipitation on ET and LAI was more than 50% in the dry sub-humid and humid zones, indicating that vegetation is rarely affected by water stress because water availability in a wet climate is not controlled by precipitation (Figure 9) [9; 40]. Low radiation and temperatures are frequently caused by excessive precipitation, which restricts the development of plants [9]. The correlation between the ecosystem indicators and temperature increases as the climate becomes suitable for vegetation growth (Figures 10 and 11). However, the climate conditions are usually cold and humid due to the low temperature, low evapotranspiration, and high precipitation (Figures 9 and 10) [40]. Vegetation growth is limited by temperature or radiation in the dry sub-humid and humid zones [66], while the negative effect on vegetation growth due to the cooling effect of precipitation reduces the sensitivity of vegetation (LAI) to temperature (Figure 11). The response of local ecosystem indicators to climate factors varies significantly. Precipitation and temperature interact to influence the changes in the ecosystem indicators. The conditions of the underlying land surface can affect the changes in the ecosystem indicators significantly. All factors such as increased coverage of natural vegetation, decreased forest area, increased arable land, and urbanization will influence ecosystem processes [9; 15; 67]. Climate change is one of the crucial contributors to the changes in the ecosystem indicators. Human activities significantly modify the ecological environment of Xinjiang. In addition to a large amount of farmland and pasture, ecological water transfer projects in the basin have also been implemented in Xinjiang [68]. Global warming and vegetation greening lead to an accelerated terrestrial carbon-water cycle [36; 69]. This study suggested that ET in the entire Xinjiang region presented a decreasing trend, whereas GPP and LAI showed an increasing trend, which is consistent with the findings of previous studies [8; 15; 20; 26; 69]. On the one hand, the inconsistent changing trends of ET and both GPP and LAI in Xinjiang may be due to the apparent differences in the sensitivity of ET to climate and vegetation changes in various zones [68]. On the other hand, the carbon cycle and vegetation growth are also affected by human activities [70]. In hyper-arid and arid zones, ecosystem indicators exhibit increasing trends. The improvement in the ecosystem indicators was mainly caused by human activities, accounting for more than 80% and 76% of the ecosystem changes, respectively. The ecosystem indicators improved mainly due to the increased area of oasis irrigation and the ecological water transfer project. The vegetation in this area was distributed primarily in the oasis, where the rapid population growth led to a dramatic expansion of farmland area [39].