## 3 Results
### Impact of ECIs on EIs During the Growing Season  
During the growing season, the ETI and DTR had the most dominant influence on the GPP. The significance of the ETI's effect on the GPP was 0.263, showing an extremely significant positive correlation (\(p<0.001\)), while DTR had a significance level of 0.172, showing an extremely significant negative correlation with GPP (\(p<0.001\)). The remaining indices were weighted similarly, with both CWD and CDD exhibiting extremely significant positive correlations with the GPP (\(p<0.001\)) (Figure 5a). The results for NDVI mirrored those for the GPP, although CWD showed an extremely significant negative correlation with the NDVI (\(p<0.001\)). All indices, except STI, were extremely significantly correlated with te NDVI (\(p<0.001\)) (Figure 5b). Figure 4: Temporal stability of ECIs in relation to EIs across different regions of SWC (annual scale). (**a**–**d**) display the temporal stability of the GPP with respect to ECIs for the HDM, SCB, YGP, and GXB regions, respectively, over a 38-year period, using 15-year intervals as a moving window. (**e**–**h**) present similar analyses, but with the NDVI as the EI. The DTR (\(-\)), ETI (\(+\)), and CWD (\(+\)) were relatively important for the GPP in the HDMs, with weights of 0.279, 0.231, and 0.186, respectively. These indices also exhibited extremely significant correlations with the GPP (\(p<0.001\)). The correlation between the GPP and CDD in the HDMs was also extremely significant and negative (\(p<0.001\)), although its weight was relatively low (0.057) (Figure 6a). In the SCB, all types of climate extremes were of comparable importance to the GPP, but only CWD showed a significant positive correlation (\(p<0.05\)) (Figure 6b). In the YGP, the ETI was the most important index, with a weight of 0.306 and an extremely significant positive correlation with the GPP (\(p<0.001\)). Other indices had moderate significance, with the CWD (\(+\), \(p<0.001\)), CDC (\(+\), \(p<0.01\)), CDI (\(-\), \(p<0.01\)), DTR (\(-\), \(p<0.05\)), and SPI (\(+\), \(p<0.05\)) showing significant correlations (Figure 6c). In the GXB, the ETI, DTR, and CWD were significantly and positively correlated with the GPP, although their weights were moderate (Figure 6d). Figure 5: Weights and temporal stability of ECIs in relation to EIs in SWC (growing season). (**a,b**) display the weights and correlations of the ECIs with the GPP and NDVI, respectively. (**c,d**) present similar information but focus on the temporal stability of ECIs over a 38-year period, using 15-year intervals as the moving window. The weights of the various indices for the NDVI was similar to those for the GPP. However, the magnitude of their correlations with the NDVI varied significantly (Figure 6e,h). NDVI showed highly significant correlations (\(p<0.001\)) with all indices except STI and CDD in the HDM, SCB and YGP. In the GXB, the NDVI exhibited extremely significant positive correlations with the CDC and WDI (\(p<0.001\)), highly significant positive correlations with the SPI (\(p<0.01\)), and highly significant negative correlations with the CDI (\(p<0.01\)). The temporal stability of the ETI (+), DTR (\(-\)), and CWD (+) during the growing season in the SWC was relatively high, with significant correlations with the GPP across the entire time series (Figure 5c). In the HDMs, the temporal stability of ECIs mirrored the overall temporal stability of their effects on Els (Figure 7a). In contrast, the temporal stability of ECIs in the SCB was lower (Figure 7b). In the YGP, the ETI (+) and CWD (+) exhibited better temporal stability (Figure 7c), while in the GXB, the DTR (+) showed good temporal stability but only up to 2016 (Figure 7d). The NDVI during the growing season was influenced by a wide range of factors. The ETI (+) and DTR (\(-\)) displayed strong temporal stability, whereas other indices experienced gaps of 15 years or more (Figure 5d).