# Satellite-Observed Global Terrestrial Vegetation Production in Response to Water Availability
## 3 Results
### Validation of LUE GPPs' Accuracy, Dynamics Trends and Drought's Effect on GPP
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{2}{c}{**Light-Use Efficiency Models**} \\ \hline
**Type** & **Statistics** & **VPD only** & \(\textbf{VPD}_{\text{CLO}}\)**-**SM** & \(\textbf{VPD}_{\text{MOD}}\)**-**SM** & \(\textbf{VPD}_{\text{CLO}}\)**-**ETR** & \(\textbf{VPD}_{\text{MOD}}\)**-**ETR** \\ \hline \multirow{2}{*}{DBF (N: 1693)} & R\({}^{2}\) & **0.7822** & 0.7467 & 0.7610 & 0.7275 & 0.7454 \\  & RMSE & **2.1887** & 2.3839 & 2.3068 & 2.4894 & 2.3932 \\ \hline \multirow{2}{*}{EBF (N: 857)} & R\({}^{2}\) & 0.6388 & 0.3798 & 0.3663 & 0.5599 & **0.6662** \\  & RMSE & 1.9865 & 2.8458 & 2.8692 & 2.5501 & **1.9500** \\ \hline \multirow{2}{*}{ENF (N: 2968)} & R\({}^{2}\) & 0.7706 & **0.7833** & 0.7733 & 0.7671 & 0.7590 \\  & RMSE & 1.6990 & **1.6399** & 1.6919 & 1.7278 & 1.7697 \\ \hline \multirow{2}{*}{MF (N: 863)} & R\({}^{2}\) & 0.8480 & **0.8479** & 0.8484 & 0.8486 & 0.8496 \\  & RMSE & 1.3900 & **1.3825** & 1.3877 & 1.3873 & 1.3904 \\ \hline \multirow{2}{*}{WET (N: 541)} & R\({}^{2}\) & **0.6860** & 0.5871 & 0.6297 & 0.5953 & 0.6406 \\  & RMSE & **2.0777** & 2.5013 & 2.3196 & 2.4670 & 2.2742 \\ \hline \multirow{2}{*}{CSH/OSH (N: 317)} & R\({}^{2}\) & 0.6563 & 0.4718 & 0.4369 & **0.6829** & 0.6609 \\  & RMSE & 1.3422 & 1.7781 & 1.8739 & **1.3185** & 1.3611 \\ \hline \multirow{2}{*}{WSA (N: 545)} & R\({}^{2}\) & **0.8103** & 0.7806 & 0.7947 & 0.7784 & 0.8001 \\  & RMSE & **1.1185** & 1.3406 & 1.2351 & 1.3736 & 1.2354 \\ \hline \multirow{2}{*}{SAV (N: 427)} & R\({}^{2}\) & **0.6776** & 0.6511 & 0.6517 & 0.6749 & 0.6746 \\  & RMSE & **1.3769** & 1.6252 & 1.6233 & 1.4901 & 1.4919 \\ \hline \multirow{2}{*}{GRA (N: 1767)} & R\({}^{2}\) & 0.7667 & 0.7727 & 0.7730 & 0.7754 & **0.7763** \\  & RMSE & 1.9214 & 1.9175 & 1.9088 & 1.9137 & **1.9012** \\ \hline \multirow{2}{*}{CRO (N: 1392)} & R\({}^{2}\) & **0.5290** & 0.4686 & 0.5047 & 0.4564 & 0.4953 \\  & RMSE & **3.5701** & & / & / & \\ \hline All sites except cropland & R\({}^{2}\) & **0.7739** & 0.7399 & 0.7427 & 0.7459 & 0.7628 \\ (N: 9978) & RMSE & **1.8089** & 1.9817 & 1.9679 & 1.9739 & 1.8855 \\ \hline \hline \end{tabular} Note:The sites are deciduous broadleaf forest (DBF), evergreen broadleaf forest (EBF), evergreen needleleaf forest (NF), mixed forest (MF), wetlands (WET), closed shrulands/open shrulands (CSH/OSH), woody savanna (WSA), savanna (SAV), grassland (GRA) and cropland (CRO), VPD only, VPD\({}_{\text{CLO}}\)-SM, VPD\({}_{\text{MOD}}\)-SM, VPD\({}_{\text{CLO}}\)-ETR and VPD\({}_{\text{MOD}}\)-ETR stand for the moisture stress algorithms. N represents the total number of data points; R\({}^{2}\) is the R\({}^{2}\) values of linear regressions with intercept. RMSE represents root mean square error. For each land-use type, the corresponding “best algorithm” is highlighted in bold.  
\end{table} 
Table 1: Regression statistics for different light-use efficiency models between each land-use type’s measured FLUXNET GPP and LUE GPPs. Figure 1: The dynamics trend and spatial distribution of the annual ensemble mean light-use efficiency (LUE) model gross primary productivities (GPPs) from 1982 to 2015. (**a**) Linear trend of annual ensemble mean LUE model GPPs. The shaded areas denote one standard deviation of each corresponding ensemble. (**b**) Spatial distribution of the linear change rate of GPP during 1982-2015. Only statistically significant trends (\(p<0.05\)) are shown in this figure. The inset shows the corresponding values’ frequency distribution. Figure 2: Drought frequency and LUE GPP changes’ spatial distribution during the drought period. (**a**) Geographical pattern of drought frequency from 1982-2015 (based on Standardized Precipitation Evapotranspiration Index (SPEI)–12 month). (**b**) GPP anomalies during drought period relative to non-drought period.