## 3 Results
### Comparisons of VPP Estimates with MODIS-LSP
\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** \\ \hline ENF & 0.74 & 0.12 & \(-\)10.60 & 4.82 & 16.04 & 3.27 & 11.51 & 0.91 & 8936 & 2389 \\ DNF & 0.40 & 0.12 & \(-\)5.94 & 3.15 & 9.73 & 2.03 & 7.21 & 1.44 & 4255 & 1256 \\ DBF & 0.84 & 0.04 & 4.95 & 1.77 & 9.79 & 0.71 & 8.28 & 0.54 & 16,160 & 4168 \\ MF & 0.78 & 0.12 & \(-\)10.2 & 5.45 & 19.52 & 2.12 & 18.74 & 2.42 & 20,662 & 5399 \\ OSH & 0.10 & 0.12 & 5.75 & 6.17 & 17.86 & 2.50 & 15.74 & 3.03 & 29,941 & 7881 \\ SAV & 0.84 & 0.03 & \(-\)4.34 & 3.84 & 13.94 & 1.67 & 12.76 & 1.20 & 61,135 & 15,842 \\ WSA & 0.87 & 0.04 & 0.39 & 3.29 & 16.51 & 2.00 & 16.19 & 2.05 & 63,596 & 16,477 \\ GRA & 0.74 & 0.04 & \(-\)12.30 & 2.01 & 25.47 & 2.66 & 22.23 & 2.54 & 25,361 & 6633 \\ WET & 0.76 & 0.09 & 9.83 & 8.43 & 15.64 & 5.37 & 10.19 & 2.22 & 5391 & 1438 \\ CRO & 0.68 & 0.07 & \(-\)0.32 & 3.65 & 23.87 & 2.55 & 23.60 & 2.61 & 34,867 & 9216 \\ URB & 0.66 & 0.07 & \(-\)5.55 & 2.91 & 18.21 & 1.79 & 17.13 & 1.58 & 2550 & 661 \\ CNV & 0.63 & 0.10 & \(-\)1.26 & 3.11 & 16.12 & 2.61 & 15.77 & 2.72 & 3156 & 870 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary statistics of the differences between starting day of GPP (SOG) estimates and MODIS-SOS 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). smaller than the RMSD values for DNF, WET, and CRO in autumn phenology, implying that these differences are primarily associated with systematic variations. The magnitudes of bias and RMSD between VPP and MODIS-LSP also varied across PFTs and climatic regions. For ENF, average SOG and MODIS-SOS occurred between DOY 110 and DOY 118 in H12V03, DOY 104 and DOY 117 in H12V04, and DOY 60 and DOY 88 days in H18V04, respectively (Figure 6). We found that the absolute magnitude of bias between SOG and MODIS-SOS increased for ENF, from boreal (a difference of 8 days in H12V03) to temperate in North America and the European Mediterranean region (a difference of 28 days in H18V04), whereas the magnitude of bias between EOG and MODIS-EOS increased for ENF with a decrease in latitude. Notably, spatial variations in bias between SOG and MODIS-SOS for MF were considerable. For MF, average SOG and MODIS-SOS were detected at DOY 142 and DOY 124 in H23V02, DOY 124 and DOY 120 in H12V04, and DOY 5 and DOY 72 in H20V08, respectively. A considerably large bias between SOG and MODIS-SOS occurred for MF in humid tropical regions (H20V08). Figure 6: Box plots showing the averaged VPP estimates and MODIS-LSP for main plant functional types in each of the seven selected tiles in 2001–2017, (**a**) H12V03, (**b**) H12V04, (**c**) H18V04, (**d**) H20V07, (**e**) H20V08, (**f**) H23V02, and (**g**) H27V05. 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). The average SOG for DBF ranged from DOY 96 to DOY 117 and occurred 4-7 days later than the MODIS-SOS, which ranged from DOY 89 to DOY 113 in temperate and European Mediterranean regions (H12V04, H18V04, and H27V05). However, the average SOG in tropical humid regions (H20V08) occurred on DOY 88, 18 days later than the MODIS-SOS (DOY 70).