## 2 Materials and Methods
### Methods  
Figure 3 shows the technical scheme, including four key steps: (1) data preprocessing, (2) STL time series decomposition, (3) analysis of the spatio-temporal variations of WUE, and (4) factor detection for the spatial pattern of WUE.  
### Methods  
Figure 3 shows the technical scheme, including four key steps: (1) data preprocessing, (2) STL time series decomposition, (3) analysis of the spatio-temporal variations of WUE, and (4) factor detection for the spatial pattern of WUE.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Serial Number** & **Factors** & **Code** & **Datasets** & **Period** & **Space Resolution** & **Time Resolution** & **Data Source** \\ \hline
1 & gross primary & GPP & MODIS GPP & 2002–2021 & 500 m & 8-day &
\begin{tabular}{c} Google Earth Engine \\ Image collection ID: \\ MODIS/006/MOD17A2H \\ \end{tabular} \\
2 & evapotranspiration & ET &
\begin{tabular}{c} MODIS ET \\ (MOD16A2.006) \\ \end{tabular} \\
3 & leaf area index & LAI &
\begin{tabular}{c} MODIS LAI \\ (MOD15A2H.061) \\ \end{tabular} \\
4 & air temperature & AT & CMFD & 2002–2018 & 0.1\({}^{\circ}\) & 3 h &
\begin{tabular}{c} Dataset Provider: TPDC \\ ([[http://data.tpdc.ac.cn/en/](http://data.tpdc.ac.cn/en/)]([http://data.tpdc.ac.cn/en/](http://data.tpdc.ac.cn/en/)) \\ data/8028b944-daa-4511- \\ 8769-96561265249/ \\ \end{tabular} \\
5 & precipitation & PR & CMFD & 2002–2018 & 0.1\({}^{\circ}\) & 3 h &
\begin{tabular}{c} dataset Provider: TPDC \\ ([[http://data.tpdc.ac.cn/en/](http://data.tpdc.ac.cn/en/)]([http://data.tpdc.ac.cn/en/](http://data.tpdc.ac.cn/en/)) \\ data/8028b944-daa-4511- \\ 8769-96561265249/ \\ \end{tabular} \\
8 & shortwave & SR & CMFD & 2002–2018 & 0.1\({}^{\circ}\) & 3 h &
\begin{tabular}{c} accessed on 15 August 2022 \\ \end{tabular} \\
9 & vegetation type & VT & \
\begin{tabular}{c} vegetation types \\ spatial distribution \\ map in China \\ \end{tabular} & 2001 & 1000 m & 1000 m & - &
\begin{tabular}{c} Dataset Provider: Resource \\ and Data Center of China \\ ([[https://www.resdc.cn/](https://www.resdc.cn/)]([https://www.resdc.cn/](https://www.resdc.cn/)) \\ data.aspx?DATAID=122, \\ accessed on 15 August 2022) \\ \end{tabular} \\
10 & soil moisture & SM & SMC & 2002–2018 & 0.05\({}^{\circ}\) & Monthly &
\begin{tabular}{c} Dataset Provider: TPDC \\ ([[http://data.tpdc.ac.cn/en/](http://data.tpdc.ac.cn/en/)]([http://data.tpdc.ac.cn/en/](http://data.tpdc.ac.cn/en/)) \\ data/34 cfeb37-75b4a6-b6-3b23 ddd4c250e/, accessed on 15 August 2022) \\ \end{tabular} \\
11 & elevation & ELE & SRTM DEM & 2000 & 90 m & - & Google Earth Engine \\
12 & slope & SLP & SRTM DEM & 2000 & 90 m & - & Image ID: \\
13 & aspect & ASP & SRTM DEM & 2000 & 90 m & - & CGIAR/SRTM90\_V4 \\
14 & slope position & SP & SRTM DEM & 2000 & 90 m & - & Dataset Provider: \\
15 & topographic & TPI & SRTM DEM & 2000 & 90 m & - & NASA/CGIAR \\ \hline \hline \end{tabular}
\end{table}
Table 1: Data description used in this study.  
Figure 3: The overall technical scheme. AT: air temperature; PR: precipitation; HUM: specific humidity; WS: wind speed; SR: shortwave radiation; VT: vegetation type; SM: soil moisture; LAI: leaf area index; ELE: elevation; SLP: slope; ASP: aspect; SP: slope position; TPI: topographic position index.