# Impacts of Drought and Heatwave on the Vegetation and Ecosystem in the Yangtze River Basin in 2022
## 3 Results
### The Response of Vegetation and Ecosystem to the 2022 Drought and Heatwave  
Our study indicates that the summer drought and heatwave in 2022 had a negative impact on vegetation productivity and ecosystem carbon balance. [PERSON] has also explored this issue and arrived at similar conclusions [39]. Tables 4 and 5 present the estimated monthly averages of various productivity metrics for the year 2022, along with their change percentages relative to the reference year. The overall analysis shows that in both tables, most cell values from July to October, except for the last column, are predominantly blue, especially in August and September. The change percentages of the last column, NEE, are red from May to August and blue from September to October. This indicates that vegetation growth conditions were reduced from their usual levels in the summer of 2022, with negative impacts on the carbon cycling system, as well. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Month** & **NDVI** & **SIF** & **GPP** & **NEE** \\ \hline January & 0.4551 & 0.02598 & 1.71776 & 0.71092 \\ February & 0.42727 & 0.03172 & 2.70615 & 0.64699 \\ March & 0.45195 & 0.06879 & 6.23024 & 1.30209 \\ April & 0.52012 & 0.14856 & 9.16238 & 0.66888 \\ May & 0.59753 & 0.24623 & 8.6162 & 0.51057 \\ June & 0.66165 & 0.31369 & 9.98955 & \(-\)0.14165 \\ July & 0.71436 & 0.35914 & 13.45568 & \(-\)1.7425 \\ August & 0.69438 & 0.3142 & 11.39368 & \(-\)1.4031 \\ September & 0.65029 & 0.21294 & 8.41859 & \(-\)0.22193 \\ October & 0.5891 & 0.12502 & 4.55401 & 0.30409 \\ November & 0.52874 & 0.06758 & 4.79452 & 0.65478 \\ December & 0.46464 & 0.03045 & 1.8233 & 0.38198 \\ \hline \hline \end{tabular}  
* In this table, the unit for GPP and NEE is gC m\({}^{-2}\) d\({}^{-1}\), and NDVI and SIF are unitless.  
\end{table} 
Table 4: Monthly average data of NDVI, SIF, GPP, and NEE for the year 2022. Red indicates an increase in the monthly average compared to the mean for the base years (2018-2021), while blue indicates a decrease. Figure 5: The seasonal cycles of different soil moisture metrics: (**a**) SM1 (unitless), (**c**) SM2 (unitless), (**e**) SM3 (unitless), and (**g**) SM4 (unitless). The corresponding change percentages for the year 2022 compared to the average values from 2018 to 2021 are shown in (**b**) SM1 (unitless), (**d**) SM2 (unitless), (**f**) SM3 (unitless), and (**h**) SM4 (unitless). In (**a,c,e,g**), the black line represents the monthly average for 2022, and the red line represents the monthly average value from 2018 to 2021. In (**b,d,f,h**), the blue part represents the proportion of value in 2022 that exceeds the average from 2018 to 2021, while the red part represents the proportion of value in 2022 that falls below the average from 2018 to 2021. By observing the differences in NDVI, SIF, and GPP during the seasons of 2022 compared to the reference year (Figure 6, Tables 4 and 5), we found that NDVI exhibited the earliest response and the longest duration, remaining below the annual average throughout July to October (Figure 6b). Although its peak values in previous years occurred in August (0.72), in 2022, it reached a relatively smaller peak value in July (0.71) (Figure 6a). In comparison, SIF and GPP were significantly higher than the annual average in July, reaching their peaks in 2022 (SIF: 0.40, GPP: 13.46), exceeding their usual peak values (SIF: 0.34, GPP: 11.67). It was not until August that SIF and GPP began to decrease below normal values, followed by a trend of returning to the reference year's levels (Figure 6c-f). However, despite SIF and GPP showing relatively delayed responses compared to NDVI during the drought and heatwave event, the severity of their damage (GPP: 17.4%, SIF: 8.7%) was significantly higher than NDVI (4.4%), which is consistent with previous research findings. Therefore, we can evaluate the advantages of SIF and NDVI in reflecting the impact of drought and heatwave on vegetation from different perspectives.