## 3 Results
### Response of Vegetation CUE and WUE to Changes in Precipitation and Temperature in the NMR  
Temperature and precipitation are critical factors influencing variations in vegetation CUE and WUE. The impacts were evaluated by calculating the partial correlation coefficients connecting temperature, precipitation, and both CUE and WUE at the pixel level (Figure 8). The association between vegetation CUE and precipitation was primarily negative (85.65%), with partial correlation values ranging from \(-\)0.809 to 0.690 (Figure 9), which had an average coefficient of \(-\)0.173. The majority of these correlations were non-significant negative correlations (80.65%). Direct relationships linking CUE to precipitation were mainly found in the northwest and southeast parts of the research region, with a specific focus on Yongzhou, Chenzhou, Guilin, Heyuan, Meizhou, and Longyan. Significant positive correlations (0.06%) were scattered across the region. Significant negative correlations (5.03%) between CUE and precipitation were detected in the southern and northeastern sections of the research region, particularly in Hezhou, Ganzhou, and Shaoguan. Similarly, the association between vegetation CUE and temperature was predominantly negative (79.56%), with partial correlation values spanning from \(-\)0.882 to 0.852 (Figure 9), which had an average coefficient of \(-\)0.195. Significant negative correlations (18.09%) were primarily detected in the southeastern regions of the research area, particularly in Hezhou, Shaoguan, Qingyuan, Heyuan, and Meizhou, while significant positive correlations (1.89%) were observed in the northwestern regions, particularly in Shaoyang and Guilin. These findings suggest that temperature exerts a stronger influence on vegetation CUE compared  
Figure 7: Sustainability of vegetation CUE (**a,b**) and WUE (**c,d**) trends in the NMR from 2001 to 2023.  
to precipitation. For vegetation WUE, the majority of the relationships with precipitation were negative (90.57%), with coefficients spanning from \(-0.869\) to \(0.638\) (Figure 9), which had a mean value of \(-0.276\). Notable inverse relationships (25.14%) between WUE and precipitation were primarily distributed in Qingyuan, Shaoguan, Heyuan, Meizhou, and Ganzhou, whereas positive correlations (9.43%) were mainly found in Guilin, Shaoyang, and Yongzhou. The association of vegetation WUE with temperature was also predominantly negative (54.92%), with the coefficients spanning from \(-0.824\) to \(0.838\) (Figure 9), which had a mean value of \(-0.019\). Notable inverse relationships (8.94%) linking WUE to temperature were identified in Zhaoqing, Shaoguan, Qingyuan, and Meizhou, while significant positive correlations (10.39%) were concentrated in Chenzhou and Ganzhou. These results indicate that, while temperature also has an effect, it is precipitation that plays a significantly more prominent role in influencing vegetation WUE. Vegetation CUE showed a predominantly inverse relationship to precipitation. The average correlation coefficients between CUE and precipitation for forest, grassland, shrub, and cropland were all negative, with grassland showing the largest negative correlation coefficient (\(-0.19\)) and shrubland the smallest (\(-0.03\)) (Figure 10). Notably, 2.88% of cropland areas demonstrated a marked inverse relationship to precipitation, covering approximately 178.48 km\({}^{2}\), the largest proportion among the four vegetation types. Additionally, shrubland exhibited a notable inverse relationship linking CUE to precipitation. Similarly, CUE and temperature were also primarily negatively correlated. Interestingly, shrubland had a mean positive correlation value of 0.55 (Figure 10), indicating a strong direct relationship linking CUE to temperature, while all other vegetation types showed negative correlations. Furthermore, 20.57% of forest areas demonstrated a marked inverse relationship linking CUE to temperature, covering approximately 8724.20 km\({}^{2}\), which was the largest proportion among the four vegetation types.