## 5 Conclusions  
In this paper, by studying the variation trends of NDVI and WUE from 2001 to 2010 and from 2011 to 2020, we discussed the variation characteristics of vegetation WUE in this region under the background of vegetation restoration. This study found that the restoration of vegetation on the Loess Plateau since the project of returning farmland to forest has promoted an increase in vegetation WUE, and the increase in WUE from 2011-2020 was more significant than that in 2001-2010. The area of the Loess Plateau with an upward trend of WUE in 2011-2020 is improved compared to the area in 2001-2010, mainly in parts of Inner Mongolia. We found that with the increase in NDVI, the proportion of the area where WUE increased simultaneously was the largest. The precipitation temperature and WUE in this area showed no significant positive correlation. The correlation indicated that the increase in vegetation was the main reason for the increase in WUE. Therefore, for the Loess Plateau in arid and semiarid regions, these findings deepen our understanding of the carbon-water coupling mechanism of vegetation, therefore offering crucial suggestions for future ecological restoration management and governance and sustainable development of vegetation on the Loess Plateau. Conceptualization, R.M. ; Data curation, R.M. and D.W.; Formal analysis, R.M. and S.L. ; visualization, X.C. and X.Y. ; Writing--original draft preparation, R.M. and H.W. ; writing--review and editing, H.W. and B.L. All authors have read and agreed to the published version of the manuscript. This research was funded by National Natural Science Foundation of China: 42141007; Special funds for the transformation of scientific and technological achievements in Inner Mongolia Autonomous Region 2021 CG0045; National Natural Science Foundation of China (NSFC. General Projects: (Grant No. 41471430). The GPP and ET datasets are available from Google Earth Engine (GEE) at [[https://developers.google.com/earth5-Sengine/datasets/catalog/CAS_IGSNRR_PML_V2_v017](https://developers.google.com/earth5-Sengine/datasets/catalog/CAS_IGSNRR_PML_V2_v017)]([https://developers.google.com/earth5-Sengine/datasets/catalog/CAS_IGSNRR_PML_V2_v017](https://developers.google.com/earth5-Sengine/datasets/catalog/CAS_IGSNRR_PML_V2_v017)), accessed on 26 June 2022. The NDVI datasets are available from GEE at [[https://developers.google.com/earth5-Sengine/datasets/catalog/MODIS_006_MOD13A1](https://developers.google.com/earth5-Sengine/datasets/catalog/MODIS_006_MOD13A1)]([https://developers.google.com/earth5-Sengine/datasets/catalog/MODIS_006_MOD13A1](https://developers.google.com/earth5-Sengine/datasets/catalog/MODIS_006_MOD13A1)), accessed on 26 June 2022. Meteorological data downloaded from the National Meteorological Science Data Center at [[http://data.cma.cn/](http://data.cma.cn/)]([http://data.cma.cn/](http://data.cma.cn/)), accessed on 26 June 2022. FLUXNET data downloaded at [[https://fluxnet.org/data/fluxnet2015-dataset/](https://fluxnet.org/data/fluxnet2015-dataset/)]([https://fluxnet.org/data/fluxnet2015-dataset/](https://fluxnet.org/data/fluxnet2015-dataset/)), accessed on 26 June 2022. The SKIM elevation data were obtained from the Interferometric Synthetic Aperture Radar sensor at [[http://srtm.csi.cgi.org/](http://srtm.csi.cgi.org/)]([http://srtm.csi.cgi.org/](http://srtm.csi.cgi.org/)), accessed on 26 June 2022. The authors declare no conflict of interest. +++ ==WARNING: Truncated because of repetitions==
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