## 5 Conclusions  
This study analyzed the spatiotemporal patterns of NDVI and NPP from 2000 to 2016 and investigated their responses to climate factors. We drew the following conclusions:  
1. There was a significant spatial heterogeneity of NDVI and NPP in the Sanjiangyuan National Park. Generally, the NDVI and NPP values were high in the southeast and low in the northwest. The Yangtze River headwater region had the lowest value of NDVI, mainly in the range of 0 to 0.3, and of NPP, mainly in the range of 0 to 100 gC/m\({}^{2}\); the Lancang River had the highest value of NDVI, mainly in the range of 0.4 to 0.8, and of NPP, mainly in the range of 100 to 250 gC/m\({}^{2}\). As for the five vegetation categories, the coniferous forests had the highest values of NDVI and NPP, followed by the shrub and meadow, while the prairie had the lowest values of NDVI and NPP.
2. There were no obvious positive or negative trends in the annual NDVI and NPP time series from 2000-2016. However, a general significant increasing trend was found during the 2000-2014 period with an average annual growth rate of 0.0022/a (\(p\) < 0.05) and 1.3824 gC/m\({}^{2}\)/a (\(p\) < 0.05). From 2000-2016, approximately 23.46% of the area showed a significant positive trend of NDVI that was mainly distributed in the prairie areas in the midlands and the north of the Yangtze River headwater region and in the midlands and the north of the Yellow River headwater region. It was determined that 24.32% of the NPP time series increased significantly, mainly distributed in the midlands and north of the Yangtze River headwater region and in the midlands and east of the Yellow River headwater region.
3. The vegetation growth in the Sanjiangyuan National Park was regulated using both water and heat conditions. The NDVI-annual average temperature correlation was stronger than NDVI-annual average temperature correlation in the three headwater regions and for all vegetation types. Increased precipitation and temperature could enhance photosynthesis and respiration for plant growth. Additionally, average temperature was an influencing factor of the change in NPP in the area, with a positive correlation with all vegetation types. However, there was no significant correlation between NPP and annual precipitation among all vegetation types, but weak positive influences on the NPP were detected in the prairie and meadow based on the unilateral significance test.
4. The response of vegetation to climate condition showed great spatial and temporal differences. The NDVI was profoundly affected by precipitation during the growing season for the study area, and was also influenced by the average temperature in May for the Yellow River headwater region, September for the Yangtze River headwater region, and July for the Lancang River headwater region. The NPP was significantly affected by temperature during the growing season for the study area. In addition, the NPP was regulated by the precipitation in July for the Yellow River and Yangtze River headwater regions.  
[PERSON] and [PERSON] designed the framework and wrote the manuscript, [PERSON] and [PERSON] provided direction for the research, [PERSON] analyzed and investigated the research, [PERSON] and [PERSON] provided the original datasets. [PERSON] and [PERSON] engaged in the funding acquisition. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the National Key Research and Development Program of China (No.2016 YFC0500205, No. 2017 YFC0503806) and the National Natural Science Foundation of China (No. 41501381).  
The authors declare no conflict of interest.