## 3 Results
### Different Responses of Vegetation to CHD Events of Varying Intensities  
The above analysis indicates that GPP exhibits significant differences in response to extreme climate events of varying intensities. Suitable temperature, moisture, and light conditions can promote an increase in GPP, whereas extreme temperatures and drought conditions can lead to a marked reduction in vegetation GPP. Particularly during the severe CHD event in 2022, vegetation in the YRB faced far greater stress than in the  
Figure 5: The box plots of vegetation-related anomalies across the corresponding grid points. The boxes indicate the 25 th and 75 th percentiles with the median between. The error bars indicate one standard deviation. The units for GPP are gC m\({}^{-2}\) day\({}^{-1}\), and for EVI are \(10^{-1}\). years 2003 and 2013, resulting in a substantial decline in GPP. In the following sections, we will focus on discussing these differences in GPP responses to the extreme CHD events of varying intensities in these three years. To unify the contributions of different variables, all climatic and vegetation-related variables were standardized using their standard deviations (STD). Figure 6 and Table 1 show the analyzed results for the whole YRB and five vegetation-dominated regions, while Figures 7-9 are the results based on grid points. For the whole YRB (Figure 6), climate factors such as T2m, SM, VPD, and DSR showed extreme anomalies in 2022, with averaged T2m and SM anomalies reaching 2.69 STD and \(-\)3.98 STD, respectively. These extreme high temperature and drought conditions intensified vegetation water loss, leading to a significant GPP decline, with negative GPP anomalies ranging from \(-\)3.05 STD to \(-\)5.97 STD. In contrast, during 2003 and 2013, although temperature and soil moisture also showed average anomalies exceeding one STD, the decrease in GPP was not apparent, and even a positive anomaly was observed in 2013. This suggests that only when climate anomalies reach a certain intensity do they have a substantial negative impact on GPP. Figure 6: The average anomalies in climatic and vegetation-related anomalies over the corresponding grid points. The blue, yellow, and red dots represent the CHD years 2003, 2013, and 2022, respectively. Panels (\(\mathbf{a}-\mathbf{g}\)) represent variables GPP\({}_{\text{COSIF}}\), GPP\({}_{\text{PlusSat}}\), EVI\({}_{\text{MODIS}}\), 2 m air temperature (T2m), soil moisture (SM), vapor pressure deficit (VPD), and downward solar radiation (DSR), respectively. All units are standard deviation. Furthermore, Figure 6 also illustrates that different vegetation types responded differently to extreme CHD events of similar intensity. In 2022, although the intensity of climate anomalies was not significantly different across the five dominant vegetation zones, the reduction in GPP showed noticeable differences. Among them, the negative impact on photosynthesis was smaller for deciduous forests and mixed forests, with a decline of GPP less than \(-2.0\) STD, while shrubs experienced the most severe decrease in GPP, ranging from \(-3.26\) STD to \(-5.41\) STD. Evergreen forests also showed a marked decline similar to that of shrubs, with a significant drop in GPP even under relatively moderate climate anomalies. This indicates that even under similar climatic conditions, different vegetation types exhibit distinct tolerance levels and responses to extreme climate events. In 2003 and 2013, the intensity of extreme climate events was lower, and the differences in GPP responses among vegetation types were also smaller. For example, GPP\({}_{\text{FluxSat}}\) data show that in 2022, the difference in GPP reductions between deciduous forests and shrubs was 3.88 STD, whereas in 2003 and 2013, this difference decreased to 0.87 and 0.51 STD, respectively (Table 1). This suggests that as the intensity of extreme climate events decreases, differences in the response among vegetation types also narrow.