## 3 Results
### The Responses of Precipitation, Temperature and Shortwave Radiation to the Variations of GPP  
We calculated the standardized sensitivity coefficients of precipitation (\(\eta_{p}\)), temperature (\(\eta_{t}\)), and shortwave radiation (\(\eta_{s}\)), the results of which were shown in Figure 6. The averages of \(\eta_{p}\), \(\eta_{t}\), and \(\eta_{s}\) were 0.11 \(\pm\) 0.15, 0.58 \(\pm\) 0.11, and 0.24 \(\pm\) 0.20, respectively. The relative contributions of precipitation (\(\xi_{p}\)), temperature (\(\xi_{t}\)), and shortwave radiation (\(\xi_{s}\)) to the changes of GPP in the YRB were shown in Figure 7. The averages of \(\xi_{p}\), \(\xi_{t}\) and \(\xi_{s}\) were 13.85 \(\pm\) 13.86%, 58.87 \(\pm\) 9.79%, and 27.07 \(\pm\) 15.92%, respectively. The proportions of precipitation, temperature, and shortwave radiation as dominant factors influencing the variation of GPP in the YRB were 2.07%, 96.69%, and 1.24%, respectively. Among the 3 climate factors, the GPP of the YRB was most sensitive to temperature changes, followed by shortwave radiation. GPP in the YRB was less sensitive to the changes in precipitation. Figure 5: The variations of GPP change rate (**a**), the significance of regression analysis (**b**), the boxplot of the GPP change rate in 12 water resource regions (**c**), and the boxplot of GPP change rate in different vegetation types (**d**). “Increase” represented that the increasing trends were significant (\(p<0.1\)). “Increase” represented that the increasing trends were insignificant (\(p>0.1\)). “Decrease” represented that the decreasing trends were significant (\(p<0.1\)). “Decrease” represented that the decreasing trends were insignificant (\(p>0.1\)). “Decrease” represented that the decreasing trends were insignificant (\(p>0.1\)). Boxplot elements: square points = mean values; horizontal lines within boxes = medians; whiskers = 1.5 times of interquartile ranges; and points outside the boxes = outliers. Purple lines represented the “zero value” lines. Figure 6: The spatial distributions of \(\eta_{p}\) (**a**), \(\eta_{t}\) (**b**) and \(\eta_{s}\) (**c**) in the YRB. Boxplots of \(\eta_{p}\), \(\eta_{t}\), and \(\eta_{s}\) in 12 water resource regions (**d**) and vegetation types (**e**). Boxplot elements: solid points = mean values; horizontal lines within boxes = medians; whiskers = 1.5 times of interquartile ranges; and “+” outside; the boxes = outliers. Blue lines represented the “zero value” lines. In the YRB, 72% of the areas had positive \(\eta_{p}\) values, indicating that in most regions GPP increases with increasing precipitation (Figure 6a). The regions that exhibited greater sensitivities to precipitation were primarily located in the upper reaches of the Yangtze River, such as the Jinsha River Basin above Shigu (JSJ-1) and the Jinsha River Basin below Shigu (JSJ-2), with averages of 0.35 \(\pm\) 0.07 and 0.29 \(\pm\) 0.08, respectively. The relative contributions of precipitation to GPP in the Jinsha River Basin above Shigu (JSJ-1) and the Jinsha River Basin below Shigu (JSJ-2) regions were significantly higher than that in other water resource regions, with \(\xi_{p}\) averages of 39.08 \(\pm\) 9.68% and 29.12 \(\pm\) 8.34% (Figure 7d). From vegetation type map (Figure 1e), it can be observed that these two water resource regions had significant proportions of grassland, which were 82.75% and 34  
respectively. Our results also indicated that grassland was more sensitive to precipitation compared to other vegetation types (Figure 6e). Figure 7e also indicated grassland had much higher \(\xi_{p}\) than other vegetation types, which was 37.12 \(\pm\) 9.83%. Results showed that GPP of the 12 water resource regions and four vegetation types in the YRB were more sensitive to temperature changes (Figure 6b,d-e). The Mintuo River Basin (MTJ) and the Yangtze River mainstream below Hukou (LM) had much higher \(\eta_{t}\) and \(\xi_{t}\) values, with averages of 0.71 \(\pm\) 0.11, 0.64 \(\pm\) 0.10, 72.14 \(\pm\) 10.04%, and 62.09 \(\pm\) 6.81%, respectively (Figures 6d and 7d).