## 5 Conclusions  
The escalating repercussions of climate change have led to a surge in droughs and heat-related events, exerting adverse effects on the photosynthetic capacity of vegetation and altering carbon cycles across the globe. These phenomena are particularly pronounced in mountainous terrains, as ecosystems at higher altitudes can be especially fragile. In this study, we analyzed the effects of atmospheric drought, soil drought, and compound drought on vegetation photosynthesis using high-resolution meteorological, SM, and SIF datasets covering the TRHR during the 2001-2020. Our main conclusions can be summarized as follows. 1. On the whole, both the SVPDI and SSMI showed increasing trends in the TRHR during the GS from 2001 to 2020. To this effect, the TRHR has been experiencing atmospheric desiccation and soil wetting due to climate warming and increased precipitation in recent decades. Atmospheric drought within the GS was predominantly distributed in the southern and eastern parts of the TRHR. Soil drought was mainly distributed in the eastern parts. The combination of atmospheric and soil droughs resulting in compound drought conditions was more common in the southern and eastern parts of the region. There was an upward trend in compound droughs in the TRHR during the GS from 2001 to 2020, which can be attributed to the disparity between intensifying rates during 2001-2011 and subsequent attenuation during 2011-2020. 2. Across the various datasets we used, CSIF, GOSIF, and RTSIF showed relatively high values in the southern and eastern parts of the TRHR, indicating better vegetation growth in these areas. The correlation coefficients between SIF and GPP reached up to 0.9 in the region as well, which indicated that SIF and GPP have an extremely stable correlation in the TRHR and further that GPP/SIF can be estimated from the available SIF/GPP. SIF showed a significant upward trend from 2001 to 2020, indicating that the vegetation of the TRHR has become significantly greener in the last 20 years, which may be due to the warming and wetting dynamics of the region having contributed to a more verdant landscape. 3. Overall, the high SVPDI and low SSMI in July substantially limited vegetation photosynthesis. According to the drought response characterization of SIF in the Yellow River source region (i.e., the eastern part of the TRHR, where there are better conditions for vegetation growth), compound droughs led to a larger decrease in SIF than individual events. The additional effect of SIF produced by compound droughs was stronger for atmospheric drought than soil drought, suggesting that SM may dominate vegetation growth in the TRHR. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/rs15204943/s1](https://www.mdpi.com/article/10.3390/rs15204943/s1)]([https://www.mdpi.com/article/10.3390/rs15204943/s1](https://www.mdpi.com/article/10.3390/rs15204943/s1)): Figure S1: Monthly average (a) temperature and (b) precipitation during 2001-2020; Figure S2: Spatial characteristics of annual mean (a,b) temperature and (c,d) precipitation during 2001-2020; Figure S3: Correlation coefficients of 1-month SSMI and different cumulative time scales of SVPDI throughout GS. Note: ''*'and ''*' indicate coefficients passing 0.1 and 0.05 significance levels, respectively; Figure S4: Compound drought magnitude index (CDMI) for July during 2001-2020 in the Yellow River source region. CDMI is expressed as the absolute value of the difference between SVPDI and the atmospheric drought threshold (0.5) in July multiplied by the absolute value of the difference between SSMI and the soil drought threshold (\(-\)0.5); Figure S5: Average precipitation versus average SIF at each grid in the TRHR during 2001-2020.