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Scattered cultivated lands in the agro-pastoral areas on the Qinghai-Tibet Plateau (QTP) cause pressure on the structure, function and evolvement of landscape and affect regional ecological sustainability. Based on niche theory, this study is the first to apply the niche breadth, niche entropy and niche overlap model to explore how the cultivated land expansion and development forms affect ecological roles from ecosystem interaction aspects from 1990 to 2015 at regional scales on the QTP. The results showed that: (1) Grassland was overall dominant in most counties, while the interface between the cultivated land and grassland showed great spatial variability and the main land use conversion occurred between them. From 1990 to 2015, the transfer percentage of grassland into cultivated land was 0.27%. (2) Results of cultivated land niche breadth and entropy indicated that at provincial scale, the occupancy rates of cultivated lands in Tibet and Xinjiang were lower than Sichuan, Gansu and Qinghai. (3) Cultivated land niche overlap exhibited by network graph revealed that Gansu, Sichuan and Qinghai had a high niche overlap over 0.994 at provincial scale. At city scale, the maximum overlap was Haibei-Guoluo and Lanzhou-Wuwei (0.999) while the minimum was Bayingol-Kizilsu Kirghiz (0.243), indicating that the development forms and competition of cultivated land between each two regions were quite different. (4) The driving forces derived by niche difference of different ecosystems showed that cultivated land niche was affected the evolution of grassland niche, and the social benefit was the leading benefit of cultivated land change. Overall, this study can assist local government in building the cultivated land management system. Moreover, the results of this study contribute to understand the characteristics and driving forces of the cultivated land evolution on the QTP, thus providing valuable decision reference for ecological protection, land use structure regulation and policy formulation. [Display omitted] • Cultivated land and grassland conversion is dominant land use change on the QTP. • The occupancy rates of cultivated lands in Tibet and Xinjiang were lowest. • Grassland niche affected the evolution of cultivated land niche. • The social benefit was the leading benefit of cultivated land change. [ABSTRACT FROM AUTHOR]