## 3 Results
### SIFc-GPP Relationship across Sites, Biones, and Years
Black asterisks indicate that the difference of mean GPP/SIFc slopes between two connected biomes is significant (***: \(p\) < 0.001; **: 0.001 \(<p\) < 0.01; *: 0.01 \(<p\) < 0.05). Compared with the GPP/CSIF slopes, the temporal variabilities of the GPP/GOSIF slopes were smaller for most biomes (Figure 5). The reduction of variability was most in those biomes that showed large interannual variabilities in the GPP/CSIF slopes (i.e., CSH, OSH and SAV). The site-variability of wetland (WET) biome expanded greatly from 2009 to 2011 compared with surrounding years and those of GPP/CSIF, and the variability of the grassland (GRA) biome also increased in 2002 and 2003. The enlarged variabilities were probably caused by underestimated GOSIF at a few flux sites in these two biomes in the given years as the median slope was higher than the median and lower than the mean from all years (Figure 5). Figure 4: Interannual variability of the slopes between CSIF and GPP across 12 biomes are similar to those in Figure 1. The explanation of the boxplot symbols is given in Figure 3. The solid line and dash line across each boxplot are the median value and mean value for the whole boxplot (biome), respectively. The number of flux tower sites for each year is shown on top of the x axis. Averaging all SIFc and GPP together by biome and ignoring the inter-site differences, strong linear relationships between GPP and SIFc were found consistently across the 12 biomes (Figure 6) and 14 years (Figure 7). Although the SIFc-GPP relationship varied among sites (see Figure 3), the SIFc-GPP relationships at the biome scale were strongly linear (\(p<0.001\)) for both CSIF and GOSIF. However, the large dispersion of the data points also suggests the large temporal (across years) and spatial (across sites) variability (see Figures 3-5). For example, the diverging relationship found in CSH was caused by the low CSIF values at the IT.Noe site (Figure S3 and Figure 6). Figure 5: Interannual variability of the slopes between GOSIF and GPP across 12 biomes. The explanation of the boxplot symbols is given in Figure 4.  
The linear SIFc-GPP relationships were SIFc dataset-dependent (Figures 6 and 7). The GPP/CSIF slopes were generally higher than GPP/GOSIF slopes for all biomes except DNF (Figure 6). Similar differences existed between GPP/CSIF slopes and GPP/GOSIF slopes for all 14 years (Figure 7). The GPP/CSIF slopes ranged from 34.86 (R\({}^{2}\) = 0.82,  
Figure 6: Scatter plots and linear regression of GPP and SIFc (CSIF and GOSIF) for 12 individual biomes at a daily scale (\(p<0.001\)). The statistical measures for the linear regression listed in the top left corner correspond to different colors. All the linear regressions were forced to go through the origin. The 12 biomes are similar to those in Figure 1.0  
Figure 1.1 Scatter plots and linear regression of GPP and SIFc (CSIF and GOSIF) for all 12 biome types year by year at a daily scale (\(p<0.001\)). The statistical measures for the linear regression listed in the top left corner correspond to different colors. All the linear regressions were forced to go through the origin. Years range from 2001 to 2014, and the last figure shows all the matched daily SIFc-GPP data. \(p\) < 0.001) to 39.29 (R\({}^{2}\) = 0.79, \(p\) < 0.001) across 14 years with a mean value of 37.64 \(\pm\) 0.32, and the value of R\({}^{2}\) ranged from 0.77 to 0.83. In contrast, the GPP/GOSIF slopes ranged from 30.65 (R\({}^{2}\) = 0.81, \(p\) < 0.001) to 35.19 (R\({}^{2}\) = 0.82, \(p\) < 0.001), with a mean value of 33.14 \(\pm\) 0.32, and the value of R\({}^{2}\) ranged from 0.78 to 0.83. It should be noticed that there were significant differences between CSIF and GOSIF products across all 12 biomes except CSH (Figures S4 and S7) as well as across all 14 years (Figure S5).