## 3 Results
### Comparisons of VPP Estimates with MODIS-LSP  
Both averaged VPPest and MODIS-LSP within seven tiles (Figure S4) were compared across different PFTs for the period 2001-2017 (Tables 3 and 4). The SOG had a strong relationship with the MODIS-SOS, except for OSH and deciduous needleleaf forest (DNF), with R < 0.5. The relationships between EOG and MODIS-EOS were relatively weaker than those between SOG and MODIS-SOS. Among all PFTs, relationships between EOG and MODIS-EOS for GRA, SVAV, MF, DBF, DNF, and WET were greater than 0.5. However, we found that the absolute bias values were relatively large for GRA, ENF, and WET in spring phenology, and for cropland/natural vegetation (CNV), WET, DNF, and ENF in autumn phenology. Figure 5: Spatial patterns of the averaged (**a**) starting day of GPP (SOG) and (**b**) ending day of GPP (EOG) for all plant functional types (except for evergreen broadleaf forest) from 2001 to 2017; (**c**) changes in average SOG with latitude, and (**d**) changes in averaged EOG with latitude. NH, Northern hemisphere; SH, Southern hemisphere. The large jumps in (**c**,**d**) were due to the opposite season between the Northern and Southern hemispheres. The RMSD value of spring phenology for deciduous forest was the lowest of all the PFTs, with a RMSD \(<\) 10 days. For GRA and CRO, RMSD values of spring phenology were relatively large at over 20 days. The remaining PFTs had spring phenology RMSD values that ranged from 10 to 20 days. In autumn phenology, RMSD values were generally higher than in spring phenology for the majority of PFTs. Similar to spring phenology, differences between EOG and MODIS-EOS for deciduous forest were considerably smaller than other PFTs with a RMSD \(<\) 12 days. The RMSD values of autumn phenology for CRO and CNV were considerably larger than other PFTs with a RMSD \(>\) 50 days. The RMSD values in autumn phenology were 15-20 days for ENF, DNF, MF, CSH, and GRA, and 20-40 days for SAVA, SWA, and urban and built-up regions (URB). The RMSD values were considerably \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline \multirow{2}{*}{**PFT**} & \multicolumn{2}{c}{**R**} & \multicolumn{2}{c}{**Bias (Days)**} & \multicolumn{2}{c}{**RMSD (Days)**} & \multicolumn{2}{c}{**RMSDb**} & \multirow{2}{*}{**N**} \\ \cline{2-2} \cline{6-10}  & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** & **Mean** & **SD** \\ \hline ENF & 0.26 & 0.10 & 9.07 & 7.04 & 17.84 & 3.65 & 14.08 & 2.12 & 8936 & 2389 \\ DNF & 0.50 & 0.16 & \(-\)17.10 & 1.62 & 17.88 & 1.57 & 5.16 & 0.60 & 4255 & 1256 \\ DBF & 0.69 & 0.10 & \(-\)5.14 & 2.85 & 11.41 & 1.67 & 9.83 & 1.48 & 16,160 & 4168 \\ MF & 0.69 & 0.14 & \(-\)7.45 & 3.69 & 15.29 & 3.34 & 13.04 & 2.49 & 20,662 & 5399 \\ OSH & 0.12 & 0.11 & 0.33 & 4.46 & 19.63 & 4.02 & 19.02 & 4.62 & 29,941 & 7881 \\ SAV & 0.28 & 0.16 & \(-\)2.35 & 6.64 & 23.98 & 2.85 & 23.02 & 2.53 & 61,135 & 15,842 \\ WSA & 0.67 & 0.10 & 0.94 & 4.55 & 25.63 & 3.46 & 25.21 & 3.61 & 63,596 & 16,477 \\ GRA & 0.73 & 0.04 & \(-\)12.23 & 2.38 & 17.47 & 1.31 & 17.28 & 1.36 & 25,361 & 6633 \\ WET & 0.50 & 0.13 & \(-\)32.86 & 7.12 & 36.86 & 7.17 & 16.56 & 2.34 & 5391 & 1438 \\ CRO & \(-\)0.33 & 0.12 & 2.73 & 7.84 & 61.62 & 6.24 & 61.07 & 6.45 & 34,867 & 9216 \\ URB & 0.31 & 0.17 & \(-\)4.09 & 4.01 & 31.36 & 3.81 & 30.80 & 4.22 & 2550 & 661 \\ CNV & 0.17 & 0.13 & \(-\)45.94 & 6.71 & 55.04 & 3.82 & 29.19 & 6.37 & 3156 & 870 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary statistics of the differences between ending day of GPP (EOG) estimates and MODIS-EOS for all plant functional types in the seven selected tiles. The annual statistics of correlation analysis in 2001–2017 are averaged (SD—standard deviation). Evergreen needle-leaf forest (ENF), deciduous needleleaf forest (DNF), deciduous broadleaf forest (DBF), mixed forest (MF), open shrublands (OSH), savannas (SAV), woody savannas (WSA), grasslands (GRA), wetlands (WET), croplands (CRO), urban and built-up regions (URB), and cropland/natural vegetation (CNV).