Response of grassland cover change to drought in the Mongolian Plateau from 2001 to 2020

The Mongolian Plateau is located in an arid and semi-arid region with fragile ecosystems and frequent drought disasters. In this case, exploring the response of the grassland cover to drought can provide a scientific basis for improving ecological environment as well as disaster prevention and mitigation. On the basis of MODIS remote sensing data and vegetation cover measurement data from 2001 to 2020, this thesis analyzed the change of grassland cover, drought distribution, and the correlation between them in the grassland area of Mongolian Plateau by adopting methods such as the decision tree classification method, the temperature condition index method, and the correlation analysis method. The results revealed the following: 1) From 2001 to 2020, the grassland area in the Mongolian Plateau showed an overall increasing trend. From 2001 to 2007, the dominant grassland coverage was from 40% to 60% and from 20% to 40%; after 2017, the dominant grassland coverage was from 60% to 80% and from 40% to 60%. Overall, there was a tendency of shift towards high coverage. Among the grasslands with different coverage, the transfer-in and transfer-out areas of the grasslands from 40% to 60% and from 20% to 40% were very large, with strong fluctuations and poor stability. 2) During these 20 years, 2001, 2007, 2010, 2017 and 2019 were the drought years in the study area, and the drought conditions in 2003, 2013, 2018, and 2020 were relatively moderate. The proportion of the medium-drought area could represent the overall drought situation in the study area to some extent. 3) As a whole, the reduction of grassland cover in the grassland area of the Mongolian plateau was positively correlated with the drought climate. The sensitivity of the grassland coverage with different vegetation types to the drought was ranked as follows: the typical grassland was larger than the desert grassland, which was larger than the meadow grassland; the grassland coverage from 20% to 60% responded more significantly to the drought.