## 5 Conclusions  
Using MODIS remote sensing data to estimate eWUE in different seasons in Inner Mongolia, the temporal and spatial characteristics of eWUE and its correlation with hydrothermal factors were quantitatively studied, and the following conclusions were drawn:  
1. From 2001 to 2020, the GPP and ET in spring, summer and autumn in this region showed increasing trends. In addition, the growth rates of GPP and ET in spring and summer were higher than those in autumn. Under the combined effect of GPP and ET, eWUE seasons showed significant decreasing trends in different regions (\(p<0.05\)), especially in summer (\(-0.045\)). In terms of spatial trend, eWUE in Inner Mongolia showed a downward trend in different seasons, but in some areas, eWUE showed an increasing trend.
2. In DNF and GRA, the average eWUE in spring and summer was significantly higher than that in autumn. In CRO, DBF, MF, SA and WSA, the mean eWUE in summer was significantly higher than that in spring and autumn. In spring and summer, the mean eWUE of DNF was the highest, which was significantly higher than that of the two forest types, DBF and MF (\(p<0.05\)), and the mean eWUE of SA was the lowest, which was significantly lower than that of other vegetation types (\(p<0.05\)).
3. In spring and autumn in Inner Mongolia, temperature and precipitation were mostly negatively connected in places with relatively high elevations, and in spring, eWUE was positively correlated with temperature in 95.096% of the area. Summer had the strongest vegetation WUE-temperature-precipitation negative correlation.
4. Except for DBF and SA in summer, the vegetation types' eWUE was negatively correlated with precipitation in other seasons. Except for grassland, the eWUE in summer was greater than that in spring and autumn among other vegetation types, and the correlation between eWUE and precipitation in summer grassland was the lowest.  
Methodology, W.L.; Software, H.Y.; Writing--Original Draft, S.W., W.W. and S.Z.; Writing--Review and Editing, Y.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Special Research Project of the China Institute of Water Resources and Hydropower Research (MK2020J11); Inner Mongolia Applied Technology Research and Development fund project (2021 GG0020, 2021 GG0050); Inner Mongolia Autonomous Region Key Research and Development and Achievement Transformation plan project (2022 YFHH0100); Yinshanbeila Grassland Eco-Hydrology National Observation and Research Station, and China Institute of Water Resources and Hydropower Research, Beijing 100038, China (grant no YSS202114). The central government guide local funding projects for scientific and technological development (2021 ZY0027); Inner Mongolia Autonomous Region \"Science and technology to Revitalize Mongolia\" action key special project (2022 EEDSKJXM004); The IWHR Research & Development Support Program (MK0145B022021) and the IWHR Internationally-oriented Talents Program.  
Not applicable.  
The authors are grateful to the editors and the anonymous reviewers for their insightful comments and helpful suggestions.  
The authors declare no conflict of interest.