## 3 Results
### Identification of Factor Attributions for Variations in ET and GPP  
#### 3.4.1 Relative Contributions of Influencing Factors  
Figures 7 and 8, respectively, show the probability density functions (PDFs) of the relative contributions of climatic factors and anthropogenic activities to the variations in ET and GPP in the four sub-regions of China. Table 3 lists the corresponding mean relative contribution values in the four sub-regions (%). These values are significantly different in the four sub-regions. The dominant driver of changes in ET is anthropogenic activities, with a mean relative contribution of 29.72% in TMon as a result of performing  
Figure 6: Trends of LAIH driven by anthropogenic activities and actual LAI from 1999 to 2018 over Mainland China. (**a,b**) are, respectively, the spatial trend and significance of LAIH over China from 1999 to 2018. (**c**) represents the slopes of LAIH and actual LAI over China from 1999 to 2018. (**d**) is the trends of LAIH and actual LAI over sub-regions in China from 1999 to 2018.  
the large-scale Grain to Green Program. No mean contribution of climatic drivers is larger than 20%. Due to dry climate and vegetation restoration, both precipitation (mean relative contribution: 36.84%) and anthropogenic activities (mean relative contribution: 26.33%) are more important than other climate factors in controlling ET trends in TCon, while temperature plays the least important role, with a mean relative contribution of 5.64% due to cold weather in this sub-region. In SubT, precipitation has the lowest contribution of 5.73% due to the generally moist climate of the study area. The relative importance of other factors for ET trends in this sub-region is ranked as follows: LAIH with 28.50% > SR with 18.37% > SH with 16.43% > WS with 15.79% > Temp with 15.15%. In TP, the most important driver of ET trends is precipitation (mean relative contribution: 38.59%), followed by vegetation restoration (mean relative contribution: 15.78%) and temperature (mean relative contribution: 13.46%). The contribution of SH ranks lowest at 9.29%. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & & **Prec** & **Temp** & **WS** & **SH** & **SR** & **LAIH** \\ \hline \multirow{3}{*}{TMon} & ET & 13.78 & 12.26 & 14.78 & 11.02 & 18.42 & 29.72 \\  & GPP & 8.84 & 5.97 & 10.87 & 7.70 & 18.85 & 47.75 \\ \cline{1-1}  & ET & 36.84 & 5.64 & 13.27 & 10.65 & 7.19 & 26.33 \\ \cline{1-1}  & GPP & 20.79 & 5.92 & 12.52 & 9.61 & 7.69 & 43.39 \\ \cline{1-1}  & ET & 5.73 & 15.15 & 15.79 & 16.43 & 18.37 & 28.50 \\ \cline{1-1}  & GPP & 4.15 & 9.67 & 14.35 & 9.42 & 14.84 & 47.55 \\ \cline{1-1}  & ET & 38.59 & 13.46 & 12.73 & 9.29 & 10.16 & 15.78 \\ \cline{1-1}  & GPP & 12.43 & 21.53 & 12.29 & 8.47 & 14.39 & 30.90 \\ \hline \end{tabular}
\end{table} 
Table 3: Mean relative contributions of influencing factors to ET and GPP variations for four sub-regions (%). TMon, TCon, SubT, and TP, respectively, represent temperate monsoonal, temperate continental, subtropical–tropical monsoonal, and high–cold Tibetan Plateau regions. Prec, Temp, WS, SH, SR, LAIH, respectively, represent precipitation, temperature, wind speed, specific humidity, solar radiation, and LAI disturbed by human activities. Figure 7: PDFs of the relative contributions of influencing factors to ET variations for four sub-regions. Prec is precipitation, Temp is temperature, WS is wind speed, SH is specific humidity, SR is solar radiation, LAIH is LAI influenced by human activities. Unlike the ET identifications, the vegetation restoration induced by human activities (with a mean relative contribution of 47.75% in TMon, 43.39% in TCon, 47.55% in SubT, and 30.90% in TP) has a much greater influence on GPP changes in the four sub-regions than climate factors.