## 3 Results
### Comparison of SIF and EVI in Response to Drought  
To further explore the difference in response of biome-specific vegetation of SIF and EVI to extreme drought, anomalies of SIF and EVI among the entire region under extreme and medium dry are shown in Figure 7. In general, the magnitude of anomalies of SIF and EVI was proportional to the mean SPEI among each category (Figure 7a,d). Tussock grasslands under the worst dry situation in 2018-2019 also exhibited the largest reduction of both SIF and EVI compared with other major biomes (Figure 7b,c). Apart from this, the largest divergent magnitude of anomalies under extreme and medium dry conditions was also shown. Relative to arid/semiarid biomes (e.g., hummock grassland, open shrubland, and scattered shrubs and grasses), mesic ecosystems (e.g., woodland, open woodland) exhibited larger differences under two drought intensities (Figure 7b,c). There was an evident trend for EVI, with the amplified difference between extreme and medium dry from arid to humid climate regimes (Figure 7f), especially for positively anomalous EVI under medium dry (AI \(>\) 0.5), mainly distributed over northern coastal areas (Figure 5). Conversely, the majority of SIF across different biome types or climate regimes showed negative anomalies with comparable magnitude, regardless of diverse drought intensity (Figure 7b,e).  
Temporal percentage of drought-related vegetation decline indicated by EVI and SIF at a monthly and 16-day scale is shown in Figure 8. At the beginning of this drought event (November 2018), approximately 38%, 20% of the area was affected by moderate (\(<\)\(-\)0.5\(\sigma\)) and severe (\(<\)\(-\)1\(\sigma\)) losses, respectively, indicated by EVI, and increased to over 80%, 50% with the development of extreme drought (Figure 8a). The percentage of moderate and severe reduction observed by SIF, \(\text{SIF}_{\text{PAR}}\) in November of 2018 was around 36%, 18%. In addition, the percentages of affected area revealed by SIF slightly decreased after reaching the peak in February of 2019, while the impacted region indicated by EVI remained growing (Figure 8a-c).  
Figure 6: Region-wide seasonal cycles and anomalies of (**a**,**c**,**g**,**i**) EVI and (**b**,**d**,**h**,**j**) SIF within four pairs of ROIs in 2018–2019. Seasonal profiles of SIF and EVI within (**e**,**f**) ROI–2 in 2012–2013 and (**k**,**l**) ROI-4 in 2015–2016. Bottom panels of each figure refer to the anomalies of SIF or EVI relative to climatology (2007–2018).  
Figure 8: (**a,b,c**) Monthly and (**d,e**) 16-day time series of the percentage of drought-induced vegetation reduction indicated by EVI, SIF, and SIF\({}_{\text{PAR}}\) under moderately (\(<\!-0.5\sigma\)), severely (\(<\!-1\sigma\)), and extremely (\(<\!-2\sigma\)) negative anomalies. \(\sigma\) indicates the standard deviation of the monthly SIF, EVI during 2007–2018 as well as 16-day SIF, EVI during 2013–2018. The text of the x-axis in Figure 9d,e refer to the day of year from November 2018 to March 2019.  
Figure 7: Boxplot of anomalies of EVI and SIF under extreme and medium dry in 2018–2019 grouped by (**b,c**) major biome types and (**e,f**) aridity index. (**a,d**) The top panel refers to the spatially mean SPEI of each category.  
To further contrast the responses of SIF and EVI at a higher temporal scale, 16-day time series of percentage of moderate/severe/extreme anomalies indicated by EVI and SIF was presented in Figure 8d,e. There was apparently a larger proportion of vegetation decline indicated by EVI than SIF at each category of anomalies, especially over 20% of the area in the middle of March (DOY = 73) which was affected by extreme (\(<\)\(-\)2\(\sigma\)) reduction observed by EVI relative to the maximum 7%, indicated by SIF at the end of February (DOY = 57). Besides, the percent of pixels with no seasonality detected by EVI was also higher than that observed by SIF.