## 3 Results  
### Mapping and Temporal Analysis of Net Ecosystem Productivity Using Remote Sensing  
Over the past two decades, the Net Ecosystem Productivity (NEP) within our study area has exhibited significant trends and distinct regional characteristics, which are discernible through cutting-edge remote-sensing technology. As delineated in Figure 3, our analysis revealed that areas with lower NEP values are predominantly concentrated in specific locales of the Xinjiang Uyghur Autonomous Region, including the Taklamakan Desert and Bayingolin Mongol Autonomous Prefecture. Similarly, decreased NEP values were observed in northwestern parts of the Inner Mongolia Autonomous Region, especially within the Alxa League. These findings indicate that unique environmental conditions prevalent in these regions, such as marked desertification and aridity, are likely contributing factors to the observed lower NEP values. The application of remote sensing in this study not only augments the spatial precision of our mapping but also facilitates a deeper understanding of the temporal dynamics of ecosystem productivity, thereby enabling a nuanced exploration of the environmental influences on ecological productivity across these diverse geographical areas.  
The findings indicate that certain regions exhibited notably high Net Ecosystem Productivity (NEP) values, underscoring a significant geographical diversity. Notably, in the Xinjiang Uyghur Autonomous Region, areas such as the Ili Kazakh Autonomous Prefecture and cities in its northwestern part, including Urumqi and Altay, stood out. In Gansu Province, the trend was observed in its eastern and central parts, including cities like Xining and Wuwei. Similarly, the Ningxia Hui Autonomous Region showed high NEP values across its territory, with cities like Yinchuan marking significant observations. Further, Hebei Province's northern city of Zhangjiakou, the Inner Mongolia Autonomous Region's eastern and northeastern parts, including Xing'an League and Hulunbuir, and several cities in the northeast region, such as Harbin and Jilin, also exhibited high NEP values. These areas commonly displayed NEP values exceeding 300 gCm\({}^{-2}\)a\({}^{-1}\) per unit area, indicating a robust ecosystem productivity.  
From a broader temporal standpoint covering the years 2000 to 2020, a general increasing trend in NEP was observed across the study area, albeit with fluctuations. The average carbon sink value rose from 56.916367 gCm\({}^{-2}\)a\({}^{-1}\) in 2000 to 101.0944 gCm\({}^{-2}\)a\({}^{-1}\) in 2005, followed by a marginal increase to 103.133156 gCm\({}^{-2}\)a\({}^{-1}\) in 2010, and it eventually reached 132.78133 gCm\({}^{-2}\)a\({}^{-1}\) in 2020. Concurrently, the average carbon source value exhibited a de creasing trajectory, declining from \(-42.685974\) gCm\({}^{-2}\)a\({}^{-1}\) in 2000 to \(-22.612026\) gCm\({}^{-2}\)a\({}^{-1}\) in 2010, and further to \(-8.049237\) gCm\({}^{-2}\)a\({}^{-1}\) in 2020.  
These observations underscore a substantial shift in the carbon balance within the region, reflecting an overall augmentation in the ecosystem's capacity to function as a carbon sink. This trend signifies positive ecological progress and bears significant implications for regional environmental management and climate change-mitigation strategies.