3.1.1. Inter-Annual Change of EVI in the Growing Season

According to the mean EVI in the growing season of IMAR from 2000 to 2015, the inter-annual change of EVI during the study period was obtained (Figure 3). In general, the mean value of EVI in IMAR showed a rising trend with a growth rate of 0.021/10a and a multi-year mean value of 0.274. Among them, the mean values of EVI in 2000, 2001, 2003–2007, and 2009–2011 were lower than that of the multi-year mean level. The mean values of EVI in 2002, 2008, and 2012–2015 were higher than the multi-year mean value. The minimum EVI (0.251) appeared in 2001, and the maximum EVI (0.301) appeared in 2012.

**Figure 3.** Inter-annual change of EVI in the study area from 2000 to 2015.

## 3.1.2. Features of Spatial Distribution of Multi-Year Mean EVI

The elevation of the study area had a characteristic of a lower height in the east and the north, and a higher height in the west and the south. The sensitivity of the vegetation to the climate gradient was strong, resulting in an uneven spatial distribution of the ecological pattern. On the whole, the EVI in the growth season showed a distribution pattern decreasing from the north to the south with a change rate of 0.28/10◦N and from the east to the west with a rate of 0.22/10◦E (Figure 4). The statistical results showed that areas with high EVI value in the growing season were mainly located in the areas of Hulunbuir, Hinggan League, Tongliao, and Chifeng, with an elevation below 1250 m, between 44◦–50◦N and 115◦–125◦E (Figure 4). On the other hand, areas with low EVI value are mainly located in Xilingol League, Ulanqab League, Baotou, Bayannur League, and Erdos. The overall EVI was lower in areas where the elevation was above 2300 m, and the vegetation types in these areas were mainly meadow steppe and desert steppe.

**Figure 4.** Spatial distribution of multi-year mean of EVI in the growing season in the study area from 2000 to 2015. (**a**) Longitude and altitude statistics; (**b**) Latitude and altitude statistics.
