## 2 Method
### Climate and Anthropogenic Variables  
The impact factors considered in this study included climatic and anthropogenic factors. Because of the impact of the hydrothermal environment and solar radiation on plant growth, the influencing factors of climate variation were selected as air temperature, precipitation, and downward shortwave radiation (SRAD). In terms of human activities, the influencing factors included carbon dioxide (CO\({}_{2}\)), aerosol optical depth (AOD), and leaf area index (LAI). Among them, CO\({}_{2}\) and AOD can partly reflect industrial production activities and LAI can partly reflect the degree of vegetation restoration and protection. Air temperature, precipitation and SRAD data were provided by the Terraclimate dataset ([[https://www.climatologylab.org/terraclimate.html](https://www.climatologylab.org/terraclimate.html)]([https://www.climatologylab.org/terraclimate.html](https://www.climatologylab.org/terraclimate.html)), accessed on 4 November 2021). Using climatically aided interpolation, the Terraclimate dataset combines the World-Clim dataset with multiple sources of coarse resolution data, generating monthly climate data at a 4 km spatial resolution. These datasets provide an important basis for large-scale ecological environment research [44]. LAI data are available from the Advanced Very-High-Resolution Radiometer. The data are based on the National Oceanic and Atmospheric Administration's climate data record (CDR) program and are produced by an artificial neural network algorithm, providing high-quality time series data for climate research [45]. CO\({}_{2}\) data are available from the greenhouse gases observing satellite (GOSAT) \"IBUKI\" ([[https://www.gosat.nies.go.jp/en/](https://www.gosat.nies.go.jp/en/)]([https://www.gosat.nies.go.jp/en/](https://www.gosat.nies.go.jp/en/)), accessed on 7 November 2021). Launched in 2019, the satellite is specially designed for the observation of greenhouse gases. The data obtained by the satellite were compared with the ground station data and proven to be reliable [46]. AOD data were provided by Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) ([[https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/](https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/)]([https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/](https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/)), accessed on 11 November 2021). MERRA-2 has been improved on the basis of its predecessor, MERRA. It assimilates AOD through multi-source observational records, including the Moderate Resolution Imaging Spectroradiometer (MODIS), the Aerosol \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**ID** & **Variables** & **Source** & **Time** & **Temporal** & **Spatial** & **Units** \\  & & **Period** & **Resolution** & **Resolution** & \\ \hline
1 & GPP & Oak Ridge National Laboratory & 1982–2016 & Monthly & 8 \(\times\) 8 km & gC/m\({}^{2}\)/day \\
2 & GPP & National Tibetan Plateau Data Center & 1982–2016 & Monthly & 0.05 \(\times\) 0.05\({}^{\circ}\) & gC/m\({}^{2}\)/day \\
3 & GPP & & Data Center & 1982–2016 & 8 days & 0.05 \(\times\) 0.05\({}^{\circ}\) & gC/m\({}^{2}\)/8 days \\
4 & GPP & FluxCom & 1982–2016 & Monthly & 0.5 \(\times\) 0.5\({}^{\circ}\) & gC/m\({}^{2}\)/day \\
5 & GPP & Global Ecology Group & 2001–2016 & 8 days & 0.05 \(\times\) 0.05\({}^{\circ}\) & gC/m\({}^{2}\)/month \\
6 & Air & Terraclimate & 1982–2015 & Monthly & 4 \(\times\) 4 km & Degree \\  & temperature & & & & (\({}^{\circ}\))/month \\
7 & Precipitation & Terraclimate & 1982–2015 & Monthly & 4 \(\times\) 4 km & mm/month \\
8 & SRAD & Terraclimate & 1980–2015 & Monthly & 4 \(\times\) 4 km & W/m\({}^{2}\)/month \\
9 & LAI & AVHRR & 1982–2015 & 8 days & 0.05 \(\times\) 0.05\({}^{\circ}\) & m\({}^{2}\)/m\({}^{2}\) \\
10 & CO\({}_{2}\) & GOSAT & 2010–2015 & Monthly & 2.5 \(\times\) 2.5\({}^{\circ}\) & ppm/month \\
11 & AOD & MERRA-2 & 1982–2015 & Monthly & 0.625 \(\times\) 0.50\({}^{\circ}\) & \(\backslash\) \\ \hline \hline \end{tabular}
\end{table}