# Evidence of Carbon Uptake Associated with Vegetation Greening Trends in Eastern China
## 5 Conclusions  
Significant greening trends in Eastern China were observed by various parameters including NDVI trends of 0.70 \(\pm\) 0.61% yr\({}^{-1}\) (MODIS) and 0.71 \(\pm\) 0.75% yr\({}^{-1}\) (AVHRR) and an EVI trend of 0.86 \(\pm\) 0.60% yr\({}^{-1}\) (MODIS). Greening trends over the northern and southern parts of EC are consistent with increased cropland area and production increase in north, and forest canopy increase in south. These have previously been attributed to the national policies of sustainable development, including intensification of agriculture and afforestation and reforestation as part of China's Grain-to-Green program [2]. Here, we show that these greening patterns are consistent with increased growing season CO\({}_{2}\) uptake in this region. Satellite-observed XCO\({}_{2}\) trends showed a corresponding increase in the carbon sink in the region of greening in EC. Significant XCO\({}_{2}\) decreases attributable to local biospheric influence during the growing period were shown using different correction methods to remove non-local, non-biospheric influence. Averaged XCO\({}_{2}\) trends across EC varied from \(-\)0.070 to \(-\)0.084 ppm yr\({}^{-1}\). Estimated local CO\({}_{2}\) uptake increases were 6.36 to 10.30 g C m\({}^{-2}\) over EC during the growing period, which is consistent with a MODIS observed GPP increase of 9.24 g C m\({}^{-2}\). These fluxes accounted for 6.4 to 10.3% of the mean biosphere flux during the GP, which is similar to percent increases in vegetation indices, 8.40 to 10.32% from 2003 to 2015. The total carbon uptake increase ranged from 28.41 to 46.04 Tg C. That could offset about 2-3% of EC's annual fossil fuel emissions. Integrated data from multiple greenhouse satellite (SCIAMACHY, GOSAT, OCO-2 or the recently launched Tansat) observations could provide a valuable method for estimating regional CO\({}_{2}\) flux change. The following are available online at [[http://www.mdpi.com/2072-4292/12/4/718/s1](http://www.mdpi.com/2072-4292/12/4/718/s1)]([http://www.mdpi.com/2072-4292/12/4/718/s1](http://www.mdpi.com/2072-4292/12/4/718/s1)). Conceptualization, L.R.W. and Z.H. ; methodology, L.R.W. and Z.H. ; formal analysis, L.R.W., Z.H. and L.L. ; software, L.L., Z.-C.Z., and M.S. ; writing--original draft preparation, Z.H. and L.R.W. ; writing--review and editing, L.R.W., Z.H. and L.L. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Key Research and Development Program of China (2016 YFA0600303), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA19080303) \begin{table}
\begin{tabular}{c c c c} \hline
**Period** & **Net Flux (g C m\({}^{-2}\) yr\({}^{-1}\))** & **Bio Flux (g C m\({}^{-2}\) yr\({}^{-1}\))** & **Fossil Flux (g C m\({}^{-2}\) yr\({}^{-1}\))** \\ \hline \multirow{2}{*}{GP} & 28.0 \(\pm\) 54.5 & \(-\)99.8 \(\pm\) 30.6 & 125.7 \(\pm\) 34.8 \\  & (22.6\% to 36.7\%) & (6.4\% to 10.3\%) & (5.1\% to 8.2\%) \\ \hline \multirow{2}{*}{Annual} & 264.15 \(\pm\) 109.85 & \(-\)70.77 \(\pm\) 36.76 & 328.48 \(\pm\) 91.38 \\  & (2.4\% to 3.9\%) & (9.0\% to 14.6\%) & (1.9\% to 3.1\%) \\ \hline \end{tabular}
\end{table} 
Table 3: Comparison of the estimated carbon uptake increase (6.36 to 10.30 g C m\({}^{-2}\)) due to greening with various posterior CO\({}_{2}\) fluxes inferred from CT 2017 for the region during the growing period (GP) and the whole year. Posterior CO\({}_{2}\) fluxes include the net flux, biosphere (Bio) flux, and fossil fuel emissions of annual mean and inter-annual variation. Negative values indicate carbon uptake and positive values indicate carbon emission. Values in parentheses compare the CO\({}_{2}\) sink enhancement as percentages of the various GP CT CO\({}_{2}\) fluxes. and the Key Research Program of Chinese Academy of Sciences (ZDRW-ZS-2019-3). [PERSON] was supported by a University of Chinese Academy of Sciences (UCAS) Joint Ph.D. Program scholarship. **Acknowledgments:** We thank [PERSON] for productive conversations regarding this analysis.