# The Response of NDVI to Climate Change in the Lowest and Hottest Basin in China
## 4 Discussion  
This study elucidates the spatiotemporal evolution of vegetation coverage in the arid region of the Turpan-Hami Basin and the intricate response mechanisms of vegetation to climatic factors and anthropogenic activities. The relevant conclusions offer multiple implications for the improvement of the theoretical framework of ecological science in arid regions and for guiding ecological restoration practices. Firstly, the significant upward trend in NDVI aligns with the global \"greening\" phenomenon observed in arid regions [14], yet localized degradation (e.g., in the western part of the basin) underscores the spatial  
Figure 8: Spatial distribution and proportion of the correlation degree between NDVI and MAT (**a**), MAP (**b**), and PET (**c**) in the Turpan-Hami Basin from 2001 to 2020.  
heterogeneity of vegetation dynamics. While traditional studies posit that vegetation dynamics in arid regions are predominantly driven by precipitation [28; 29], this study found that in the Turpan-Hami Basin, which is an arid region, the impact of precipitation on NDVI is highly limited due to low precipitation (75.4% of the area shows no correlation). Precipitation only exhibits a short-term water activation effect in the northwestern piedmont zones and northeastern riparian grassland zones, where strong positive correlations account for merely 4.4% of the total area and weak positive correlations account for 19.4%. These results corroborate the \"precipitation threshold effect\" hypothesis [15], which posits that when precipitation falls below the ecological water requirement threshold, vegetation dynamics are more regulated by non-climatic factors (e.g., groundwater or human irrigation) rather than responding directly to precipitation fluctuations. [PERSON] et al. confirmed through soil moisture observation networks that in extremely arid regions, vegetation water use relies predominantly on groundwater or snowmelt recharge rather than direct precipitation input [30], which also explains the localized positive correlation between NDVI and precipitation in the piedmont area observed in this study (attributable to runoff recharge effects). It is worth noting that the pronounced diurnal variations in shallow soil heat flux (SHF) can indirectly regulate vegetation-available water by influencing soil microclimate and evaporation processes [31]. Furthermore, vegetation responses to temperature changes are also strongly constrained. The positive response of NDVI to temperature is restricted to high-altitude cool regions (2.9%), suggesting that temperature increases may enhance vegetation activity by extending the growing season [32]. However, in low-altitude areas, temperature increases have an inhibitory effect due to heightened evapotranspiration. This altitudinal gradient response pattern aligns closely with the temperature sensitivity ecological threshold theory proposed by [PERSON] et al. [33]. Against the backdrop of climate change, [PERSON] et al. pointed out that there is a climate effect on the green development of vegetation in China, and the sensitivity of land surface temperature to vegetation shows significant changing trends, which may play a role in regulating land surface temperature [34]. This is echoed in this study by the complex relationship between vegetation and temperature changes in the arid Turpan-Hami Basin, further indicating that in arid regions, the interaction between vegetation and temperature may present a unique response pattern due to the particularity of the regional ecological environment (such as water availability and elevation). Secondly, PET exhibited weak positive correlations with NDVI across 37% of the study area and strong positive correlations in 9.8% of the region, challenging the traditional paradigm that evapotranspiration characterizes water stress in research [13]. For instance, [PERSON] et al. found that increased PET exacerbates water deficits and inhibits vegetation growth in the Sahel region of Africa [35].