# Monitoring Vegetation Change and Its Potential Drivers in Inner Mongolia from 2000 to 2019
## 3 Results
### Spatial Variability of NDVI
#### 3.2.3 Evaluation of Estimated Breakpoints and Trends  
STM was applied to the NDVI sequences in Inner Mongolia, and the number of breakpoints and trend changes before and after the mutations and corresponding significance levels were calculated (Figures 6 and 7). Considering the variations, approximately 16.49% of breakpoints occurred during 2002-2005, mainly in Genhe, Hulunbuir, the central Alxa League, southern Baotou, Bayannur, and northwestern Hohhot. Approximately 9.17% of the breakpoints were observed during 2005-2008, concentrated in the Alxa Right Banner and the northwestern part of Erdos. However, most of the pixels mutated during 2008-2011, distributed in the territory of the Alxa League. Finally, the largest number of pixels mutated during 2011-2014, accounting for 29.34% of all breakpoints, most of which were distributed in the areas of the Alxa League and Ordos, as well as a small part in the northeast of Hulunbuir. The remaining 22.35% of the pixels mutated during 2014-2017 and were concentrated in the southeastern part of the Alxa League, Baotou, and the northern part of Wulanchabu.  
Figure 6: Spatial distribution for breakpoints years of NDVI in Inner Mongolia during 2000–2019.  
According to the trends and the significance of changes before and after the mutations, we divided the trends into three levels of \"increased,\" \"stable,\" and \"decreased.\" The vegetation changes in the southeastern part of Alexa League, northwestern part of Bayannur, and most parts of Ordos before the mutation showed a significant upward trend. An obvious decreasing trend was observed in the south-central and eastern part of Alxa Left Banner, the south-central part of Ulanqab, Erguna, and Genhe of Hulunbeier, while the vegetation in the areas along the northwestern border of Baotou and Ulanqab showed a stable NDVI. Meanwhile, the areas with significantly increasing vegetation trends after the mutation occurred in the northern part of Alxa League, the northwestern part of Bayannur, and the border areas of Baotou and Ulanqab. The areas with significantly decreasing trends were in the central and eastern parts of Alxa League. Northwestern Hulunbeier, northern Hohhot, southern Ordos, and northwestern Bayannur, as well as small areas in Xing'an League, Tongliao, and Chifeng showed stable NDVI trends after mutation.  
The spatial distribution of NDVI trends before and after the mutation shows obvious variability. For example, most pixels in the south-central region of Alxa League showed a significant increasing trend before an abrupt change to a decreasing trend after the mutation. Meanwhile, the NDVI values at the borders of Baotou and Ulanqab changed from a stable trend to an obvious increasing trend after the mutation, and the NDVI trends in most of the central-eastern parts of Inner Mongolia, which originally showed obvious decreases, gradually stabilized after the mutation. The occurrence of breakpoint years and the differences in the trends before, and after, the mutation may indicate changes in the potential influence mechanisms of NDVI in Inner Mongolia.