## 2 Materials and Methods
### Data Collection  
In this study, we selected 2000 and 2020 as representative years to collect and analyze data. The data encompass both spatial and statistical information. The spatial data were processed at a grid cell resolution of 1 km \(\times\) 1 km, while statistical data were aggregated at the county level. Table 1 provides a comprehensive list of the primary data required to calculate the ES indicators. To ensure consistency, all spatial data were transformed to a common spatial reference system, specifically the WGS84 coordinate system and Albers equal-area conic projection. The flowchart depicted in Figure 2 illustrates the methodology that we employed to achieve our study objectives.  
\begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**ES Variable** & **Data Type** & \begin{tabular}{c} **Spatial** \\ **Resolution** \\ \end{tabular} & **Data Source** \\ \hline Land use/land cover & Raster & 30 m & \begin{tabular}{c} National Geomatics Center of China \\ ([[http://www.globallandcover.com/GLC30](http://www.globallandcover.com/GLC30) Download/index.aspx]([http://www.globallandcover.com/GLC30](http://www.globallandcover.com/GLC30) Download/index.aspx), accessed on 11 December 2020) \\ National Aeronautics and Space Administration and United States \\ \end{tabular} \\ NDVI & Raster & 250 m & \begin{tabular}{c} National Geomatics Center of China \\ accessed on 11 December 2020 \\ National Aeronautics and Space Administration and United States \\ \end{tabular} \\ DEM & Raster & 90 m & \begin{tabular}{c} Geographical Data Cloud ([[https://www.gscloud.cn/#page1](https://www.gscloud.cn/#page1)]([https://www.gscloud.cn/#page1](https://www.gscloud.cn/#page1)), accessed on 20 December 2020) \\ China Meteorological data \\ \end{tabular} \\ Meteorological data & Numeric & Sites & \begin{tabular}{c} China Meteorological Data Sharing Service System \\ ([[http://www.escience.gov.cn/metadata/page/index.html](http://www.escience.gov.cn/metadata/page/index.html)]([http://www.escience.gov.cn/metadata/page/index.html](http://www.escience.gov.cn/metadata/page/index.html)), accessed on 5 November 2020) \\ Harmonized World Soil Database \\ \end{tabular} \\ Soil database & Raster & 30 arc-second & \
\begin{tabular}{c} ([[http://www.fao.org/soils-portal/soil-survey/soil-maps-and-databases/harmonioned-world-soil-datebse-v12/en/](http://www.fao.org/soils-portal/soil-survey/soil-maps-and-databases/harmonioned-world-soil-datebse-v12/en/)]([http://www.fao.org/soils-portal/soil-survey/soil-maps-and-databases/harmonioned-world-soil-datebse-v12/en/](http://www.fao.org/soils-portal/soil-survey/soil-maps-and-databases/harmonioned-world-soil-datebse-v12/en/)), accessed on 1 December 2020) \\ National Geomatics Center of China \\ \end{tabular} \\ Administrative map & Vector & County &
\begin{tabular}{c} National Geomatics Center of China \\ ([[http://ngcc.sbsm.gov.cn/ngcc/](http://ngcc.sbsm.gov.cn/ngcc/)]([http://ngcc.sbsm.gov.cn/ngcc/](http://ngcc.sbsm.gov.cn/ngcc/)), accessed on 11 December 2020) \\ \end{tabular} \\ Crop yield, GDP and population & Numeric & County & Statistical Yearbook \\ \hline \hline \end{tabular}
\end{table}
Table 1: Datasets used in the study.  
Figure 2: Flowchart of the proposed methodology.