Abstract: As a typical inland arid and semi-arid region, ecosystem quality (EQ) change of Mongolian Plateau is the most direct indicator of global and regional climate change and human activities. Under the background of climate warming, clarifying the spatiotemporal variations and driving factors of EQ in Mongolian Plateau is of great significance for coping with climate change and improving the quality of ecological environment in Mongolian Plateau. This study evaluated the spatiotemporal variations of EQ in different ecoregions of Mongolian Plateau from 2001 to 2019 by constructing a comprehensive ecosystem quality evaluation model, and quantified the role of climate factors and human activities. The results showed that the spatial distribution of EQ in Mongolian Plateau from 2001 to 2019 was characterized by a pattern of high in the northeast and low in the southwest, with an average annual EQ value of 50.89. The mixed forests had the highest mean value of EQ, followed by coniferous forests. Due to the synergistic effects of climate change and human activities, the overall EQ showed an improvement trend at a rate of 0.48 a^-1 during the study period, with a significantly improved area accounting for 31.07%. There was strong spatiotemporal heterogeneity in the EQ of Mongolian Plateau, and the variation coefficient gradually decreased from the central typical steppe to the north (coniferous and deciduous forests) and south (deserts), with the most moderate fluctuation areas accounting for 30.69% of the whole region. Precipitation played a dominant role among the influencing factors, especially in the central and eastern typical steppes, as well as the northwestern forest steppes. Human activities showed a positive impact on the EQ from 2001 to 2019. Ecological restoration projects, such as reforestation and desertification control, promoted the improvement of the EQ.

Key words: Mongolian Plateau, ecosystem quality, spatiotemporal pattern, climate change, human activity.