## 4 Discussion  
### Differences and Variations Between \(S_{\text{GFP}}\) and \(S_{\text{ER}}\)  
Our study found no significant differences between \(S_{\text{GFP}}\) and \(S_{\text{ER}}\) (Figure 3A,B), indicating a comparable level of responsiveness to changes in precipitation. A precipitation manipulation experiment conducted on the Tibetan Plateau demonstrated that under extreme drought conditions, GPP and ER decreased by 17.26% and 19.05%, respectively, relative to the control, thereby providing indirect support for our findings [44]. The similarity in the responses of GPP and ER to precipitation changes may arise from their intrinsic connection. Physiologically, photosynthesis and respiration in plants are interrelated processes [45, 46]. The energy required for photosynthesis, derived from the respiratory breakdown of organic matter, leads to the accumulation of stable compounds when photosynthesis exceeds respiration, thereby providing a consistent substrate for respiration [47, 48, 46]. On the other hand, stomatal conductance regulates the exchange of CO\({}_{2}\), O\({}_{2}\), and H\({}_{2}\)O. Under drought stress, stomata close to reduce transpiration [49, 50, 51], impacting gas exchange and consequently affecting both photosynthesis and respiration. Eologically, studies have confirmed a close relationship between GPP and ER at regional and global scales, primarily because productivity serves as the main and direct substrate supplier for respiration, fundamentally constraining ER [52, 53]. However, the overall variation in \(S_{\text{GFP}}\) was greater than that of \(S_{\text{ER}}\) (Figure 3C), indicating that GPP was more sensitive to changes in precipitation compared to ER, a conclusion  
Figure 10: The main factors influencing the sensitivity of gross primary productivity and ecosystem respiration to precipitation (\(S_{\text{GFP}}\) and \(S_{\text{ER}}\)) across different ecosystems: (**A**) grassland \(S_{\text{ER}}\) and mean annual precipitation (MAP), (**B**) grassland \(S_{\text{GFP}}\) and mean annual precipitation, (**C**) grassland \(S_{\text{ER}}\) and mean annual temperature (MAT), (**D**) wetland \(S_{\text{GFP}}\) and MAT, and (**E**) grassland \(S_{\text{ER}}\) and vapor pressure deficit (VPD). Note: for the statistical analysis, we selected sites with at least 10 years of data within each ecosystem, rather than using all available sites within each ecosystem. that was further supported by research on the impact of water availability on carbon dioxide flux in grassland ecosystems [44; 54; 55]. This may be attributed to several factors. First, the composition of ecosystem ER is complex, consisting of both autotrophic respiration (\(R_{\mathrm{a}}\)) and heterotrophic respiration (\(R_{\mathrm{h}}\)), which may exhibit different sensitivities to changes in precipitation. This is because \(R_{\mathrm{a}}\) is more dependent on photosynthetic products [23] and photosynthesis is easily affected by precipitation [56; 57]. Furthermore, existing research indicates that the sensitivity of aboveground plant respiration to precipitation exceeds that of belowground respiration, which is in turn more sensitive than microbial respiration [44]. This suggests that the greater stability of ER in response to water variations, compared to gross primary GPP, was primarily due to the relative stability of soil or heterotrophic respiration. Secondly, multiple researchers have indicated that GPP exhibits a greater response amplitude to precipitation fluctuations. For instance, a controlled experiment conducted in temperate grassland demonstrated that GPP increased more than ER in response to increased precipitation [54]. Additionally, research based on eddy covariance measurements has shown that GPP was more sensitive to precipitation, contributing more to NEE responses than ER [53; 58]. GPP is more susceptible to changes in precipitation, which may be attributed to the role of H\({}_{2}\)O as a substrate for light reactions.