# Vegetation Health in China Is Severely Compromised by Drought, Wet and Heat Stress Events
## 3 Results
### Responses of Vegetation Health to Stress Events
#### 3.3.2 Vegetation Health Dominated by Negative Sensitivity to Stress Events  
The VHI exhibits overall negative sensitivity to stress events. Specifically, the VHI shows almost no or negative sensitivity to SPEI CD (Figure 8a,e,i,m,q), while its sensitivity to SM CD, CPA, and CH stress events is very strong. In 2001, the Northeast Plain, in 2005, the South China region, and in 2010, the Yunnan-Guizhou Plateau and the Northeast Plain exhibited strong negative sensitivity of VHI to SM CD, with proportions reaching 47.47%, 35.63%, and 46.96%, respectively. However, in 2015 and 2020, this negative sensitivity significantly decreased or turned into positive sensitivity with the negative sensitivity proportions dropping to 23.67% and 32.67%, respectively. The South China region showed increasing negative sensitivity to SM CD, while the central and northern regions gradually shifted to positive sensitivity, indicating that SM CD stress is intensifying in South China while weakening in other regions (Figure 8b,f,i,n,r). The negative sensitivity of VHI to CPA is primarily concentrated in the South China region and the Loess Plateau. In the South China region, extreme rainfall events and natural disasters such as typhoons negatively impact vegetation health. In the Loess Plateau, precipitation-induced soil erosion leads to vegetation degradation, thereby reducing vegetation health. In 2015, the negative sensitivity to CPA was significantly greater  
Figure 7: Anomalies in vegetation health due to stress events and latitudinal variation. (**a–e**) depict the abnormal changes in vegetation health due to stress events and latitudinal variation in different subregions for the years 2001, 2005, 2010, 2015, and 2020, respectively. Upright triangles represent positive anomalies, inverted triangles represent negative anomalies, and the gray dashed line indicates VHI = 0.4, serving as the threshold for vegetation health. than the positive sensitivity, accounting for 67.82%, with the central and northern regions increasingly showing negative sensitivity of VHI to CPA. CH exhibits the most pronounced sensitivity to vegetation health, with 59.21% of vegetation health nationwide showing negative sensitivity to CH. In 2005, 81.61% of VHI exhibited negative sensitivity to CH, which was particularly evident in regions below 35 degrees latitude. By 2015, the negative sensitivity of VHI to CH increased to 83.57%, significantly surpassing the negative sensitivity to other stress events, although no extreme phenomena were observed (Figure 8p). By 2020, 49.6% of regions displayed a positive sensitivity of VHI to CH, especially in South China, the Qinghai-Tibet Plateau, and parts of Heilongjiang. Overall, VHI's negative sensitivity to CH is the most pronounced, aligning with the impacts of global warming. In addition, this study analyzed the sensitivity of different vegetation types to various stress events. In 2001, the vegetation with the highest negative sensitivity to SM CD was MCBF, with a value of \(-\)39.22, followed by TK, which showed significant negative sensitivity to CH. Conversely, AV exhibited the strongest positive sensitivity to CH with a value of 9.7 (Figure 9a). In 2005, vegetation overall exhibited the strongest sensitivity to  
Figure 8: Sensitivity of vegetation health to stress events. (**a**,**e**,**i**,**m**,**q**), (**b**,**f**,**j**,**n**,**r**), (**c**,**g**,**k**,**o**,**s**), and (**d**,**h**,**l**,**p**,**t**) represent the sensitivity of vegetation health to SPEI CD, SM CD, CPA, and CH, respectively. CH with TK demonstrating the most pronounced negative sensitivity and SL showing the highest positive sensitivity (Figure 9b). In 2010, MCBF and MD exhibited strong sensitivity to CH and SM CD, respectively. Specifically, AV had a negative sensitivity to CH reaching \(-39.19\), while MD's sensitivity to SM CD and CH was \(-15.54\) and \(-15.78\), respectively.