## 5 Conclusions  
This study examined the spatio-temporal variations of vegetation phenology and GPP at seasonal and annual scales in the SRYR using 19-year remote sensing data and explored the impacts of vegetation phenology and photosynthetic carbon uptake capacity on seasonal and annual GPP. We found that not only spring phenology (SOS) but also summer phenology (POS) significantly advanced in the SRYR. The start (SOS) and peak (POS) of the growing season from 2001 to 2019 experienced significantly advanced trends (\(p<0.05\)) at rates of 0.41 d yr\({}^{-1}\) and 0.39 d yr\({}^{-1}\), respectively. The increased spring and summer air temperatures were the dominant climate factors for the advanced SOS and POS, respectively. Spring GPP showed a significantly increasing trend (\(p<0.01\)) at a rate of 0.50 g\(\cdot\)C\(\cdot\)m\({}^{-2}\cdot\)yr\({}^{-1}\), and the earlier SOS had obvious positive effects on GPP\({}_{\text{spr}}\), with a one-day advance in SOS increasing GPP\({}_{\text{spr}}\) by 0.75 g\(\cdot\)C\(\cdot\)m\({}^{-2}\). Summer GPP was significantly and negatively correlated to POS (\(p<0.05\)), and a one-day advance in POS increased GPP\({}_{\text{sum}}\) by 3.73 g\(\cdot\)C\(\cdot\)m\({}^{-2}\). Earlier start and peak of growing season had significantly positive effects on spring GPP and summer GPP, respectively. Moreover, maximum carbon uptake capacity (GPP\({}_{\text{max}}\)) had significant and positive correlations with GPP\({}_{\text{sum}}\) and GPP\({}_{\text{ann}}\) (\(p<0.01\)). It was found that earlier an spring-summer phenology and higher photosynthetic peak altered the seasonal patterns of vegetation productivity in the SRYR. Most of the existing studies focused on the effects of spring and autumn phenology on annual productivity in the QPT. The main objective of this study was to explore the effects of vegetation phenology, including peak greenness timing (POS) and photosynthetic capacity on seasonal GPP. This study suggested that not only spring and autumn phenology but also summer phenology and maximum carbon uptake capacity should be regarded as crucial indicators regulating the carbon uptake process in alpine ecosystems. This research provides important information about the response characteristics of ecosystem productivity to phenology changes for alpine ecosystems under global climate warming. Further studies are still needed to assess and reduce the uncertainty associated with the remote sensing phenology and productivity products.  
Conceptualization, F.Y. and T.L.; methodology, F.Y., C.L., Q.C. and J.L.; formal analysis, F.Y. and Q.C.; writing--original draft preparation, F.Y.; writing--review and editing, C.L.  
J.L. and T.L.; funding acquisition, T.L. All authors have read and agreed to the published version of the manuscript.  
This work is supported by National Natural Sciences Foundation of China (No. 42071038).  
Data Availability Statement: Data are contained within the article.  
We thank the Land Processes Distributed Active Archive Center for providing MODIS satellite data. We thank the China Meteorological Data Service Center for providing meteorological data.  
The authors declare no conflicts of interest.