# Impacts of Drought and Heatwave on the Vegetation and Ecosystem in the Yangtze River Basin in 2022
## 3 Results
### Response of Different Types of Vegetation during Drought and Heatwave  
As previously mentioned, based on the land cover types delineated by MODIS in the Yangtze River Basin, we selected the following two representative vegetation types: forest and cropland. In Figure 9, the forest is represented by green, while cropland is represented by purple. During the 2022 drought and heatwave period, the variation in temperature (Figure 9a) between forest and cropland ecosystems was not significantly different, indicating a similar severity of the heatwave. Regarding precipitation, except for a significant decrease in cropland compared to forest from May to June, resulting in cropland SM1 and SM2 being lower than forest during almost the same period, the precipitation patterns between forest and cropland within the study period (July-October) were almost identical (Figure 9b). Therefore, we believe that the severity of the drought and heatwave in the forest and cropland ecosystems is also similar. Under such temperature and precipitation conditions, the soil moisture values of the four layers in cropland were consistently lower than those in the forest from July to October (Figure 9c-f).  
Figure 8: Spatial distribution of partial correlations between July and October 2022: (**a**) correlations between SM1 anomalies and SIF anomalies, (**b**) correlations between VPD anomalies and SIF anomalies. The blue part represents a positive correlation, while the red part represents a negative correlation.  
For vegetation indices, during the same period (August-October), the reduction in NDVI, SIF, and GPP in cropland was significantly higher than in forest (Figure 10). This indicates that the growth status (greenness) of the forest was superior to cropland in the later stages of the drought and heatwave, suggesting that forests have a stronger self-protection ability when facing extreme climatic conditions. This is consistent with the performance of soil moisture, indicating the mutual influence between them; vegetation growth is influenced by the water absorbed from the soil by roots, and the maintenance of soil moisture also requires the stability of vegetation roots.  
Furthermore, from July to October, the NEE value of forest was consistently lower than that of cropland. This indicates that the forest ecosystem has a stronger carbon sequestration capacity during this period, while the carbon fixation capacity of cropland is relatively  
Figure 10: The differential values of the seasonal cycles for the year 2022 compared to the average values from 2018 to 2021: (**a**) NDVI (unitless), (**b**) SIF (unitless), (**c**) GPP (gC m\({}^{-2}\) d\({}^{-1}\)), and (**d**) NEE (gC m\({}^{-2}\) d\({}^{-1}\)). The green line represents forest, while the purple line represents cropland.  
Figure 9: The differential values of the seasonal cycles for the year 2022 compared to the average values from 2018 to 2021: (**a**) temperature(\(\kappa\)), (**b**) precipitation(mm), and (**c–f**) SM1–SM4 (unitless). The green line represents forest while the purple line represents cropland.  
weaker. Combined with the analysis of the changes in NDVI, SIF, and GPP discussed earlier, it can be inferred that cropland is more susceptible to the impacts of drought and heatwave events, while forests exhibit stronger self-regulation abilities (i.e., lower sensitivity to compound drought and heatwave events).