## 3 Results
### Spatial Distribution of Vegetation NPP  
To reveal the changes in the different levels of vegetation NPP across different periods, we divided this study into two periods: 2000-2010 and 2011-2022, as shown in Appendix A Figure A2 and FigureA3.  
Appendix A Figure A2a and FigureA3a showed that from 2000 to 2010, zones with levels II and III accounted for the largest proportion at 36.56%, which were mainly distributed across the Weihe Plain, Lesser Khingan, southern Henan, and northern Anhui. Secondly, zones with level I converted to zones with level II accounted for 28.06%, mostly concentrated in eastern Inner Mongolia, northern Shaanxi, and southern Qinghai Province. Areas comprising moderate to severe lushness accounted for 15.41%, being mainly distributed in southern Shaanxi, western Hunan, and southern Guangxi. During 2000-2010, zones  
Figure 5: Annual average vegetation NPP in China over the last 23 years.  
with levels I and II to zones with levels III, IV, and V had the largest area, indicating that vegetation NPP showed an overall increasing trend.  
Appendix A Figure A2b and Figure A3b showed that from 2011 to 2022, in the area where the vegetation NPP level changes, the area transferred from zones with level II to zones with level III accounted for the largest proportion, comprising 34.90%, which was mainly distributed in the Changbai Mountains, Shanxi Province, and western Shandong. The area transferred from zones with level III to zones with level IV accounted for 20.42%, mostly distributed in the Sichuan Basin and the Liaodong Peninsula. The area transferred from zones with level IV to zones with level V accounted for 16.45%, being mostly located in the western part of Guizhou, the central part of Hubei, and the junction of Heilongjiang and eastern Jilin. During 2011-2022, the area of zones with level II to zones with levels III, IV, and V accounted for the largest proportion, indicating that the overall NPP of vegetation showed an increasing trend. Overall, the vegetation NPP showed an increasing trend during 2000-2022.  
Appendix A Figure A4 and Figure A5 showed that from 2000 to 2010, the average NPP of vegetation in China ranged from 0 to 1959 gC\(\cdot\)m\({}^{-2}\cdot\)a\({}^{-1}\). The area proportion of level I was the largest, comprising 40.5%, which was mostly concentrated in the Qinghai-Tibet Plateau, Inner Mongolia, and other regions. Level V zones accounted for 3.2%, being mainly distributed in southern China, such as southern Fujian Province and the Guangxi Zhuang Autonomous Region. The area proportion of level III zones was 21.6%, being mostly concentrated in central and southern China, such as the Sichuan Basin and Hunan Province. Appendix A Figure A4 shows that the average annual NPP of vegetation in China from 2011 to 2022 had a similar trend to the average NPP of vegetation from 2000 to 2010. The difference is that the proportion of level I and level II zones decreased, and the proportion of level III zones and above had increased. When combined with our quantitative analysis in Appendix A Figure A5, in 2000-2010 and 2011-2022, we found that level I zones accounted for 40.5% and 38.4%, respectively, and the level V zones accounted for 3.2% and 3.6%, respectively.