## 5 Conclusions  
In summary, we investigated the spatial and temporal responses of SIF and EVI of dryland vegetation to the 2018-2019 extreme drought over Australia using multi-source satellite-based SIF observations. In contrast to the enhanced magnitude of reduction of both SIF and EVI in conjunction with increasing drought severity over humid/sub-humid biomes, the two vegetation variables of arid/semiarid vegetation showed comparable negative anomalies regardless of extreme or medium dry conditions, indicating the largest sensitivity and vulnerability of semiarid ecosystems to the hydroclimatic variations. At a 16-day interval, both satellite-based indicators (SIF and EVI) can synchronously detect the impact of extreme drought on dryland vegetation growth. Besides, we find that space-borne SIF is capable of characterizing the spatiotemporal dynamics of drought over water-limited ecosystems despite high retrieval noises, as compared with EVI. The unprecedented SIF derived from TROPOMI shows remarkably enhanced agreement with tower-based GPP in the dry year of 2018-2019, demonstrating the great potential of the advanced dataset to track the dynamics of dryland vegetation under future changing climates. In addition, semiarid ecosystems exhibiting the largest reduction, regardless of drought severity and time scales, are the most sensitive to climatic extremes.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/rs14071581/s1](https://www.mdpi.com/article/10.3390/rs14071581/s1)]([https://www.mdpi.com/article/10.3390/rs14071581/s1](https://www.mdpi.com/article/10.3390/rs14071581/s1)), Figure S1: Spatial pattern of drought intensity based on SPEI\({}_{\text{6-month}}\) during 2018-2019, 2015-2016, and 2012-2013 monsoon season. Green and blue rectangles refer to the region of interest (ROI). Black triangles refer to five flux tower sites.  
Conceptualization, S.L. and A.H.; methodology, S.L.; validation, S.L.; formal analysis, S.L.; investigation, S.L.; data curation, S.L., S.G. and J.C.; writing--original draft preparation, S.L.; writing--review and editing, A.H., Q.Y., X.M., J.Q., R.Z. and Q.W.; visualization, S.L. and Q.W.; supervision, A.H. and Q.Y.; funding acquisition, Q.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Natural Science Foundation of Fujian Province (2021)J01627) and the National Natural Science Foundation of China (41601562).  
Not applicable.  
**Data Availability Statement:** All satellite-based data well as other datasets in this study are available from the corresponding author upon reasonable request.  
**Acknowledgments:** This work was supported by the Natural Science Foundation of Fujian Province (2021J01627) and the National Natural Science Foundation of China (No. 41601562) for funding this work. The first author acknowledges the financial support from Chinese Scholarship Council, Ministry of Education, China. We also would like to thank the opening of flux tower data for public access by the Australian Terrestrial Ecosystem Research Network (TERN, Available online: www.tern.org.au (accessed on 30 June 2020))--OzFlux facility (Available online: www.ozflux.org.au (accessed on 30 June 2020)).  
**Conflicts of Interest:** The authors declare no conflict of interest.