The research was conducted at Tongliao,Inner Mongolia Autonomous Region, which was a typical part of the Agro-pastoral Transitional zone of North China, for three plant-growing seasons between 2003 to 2005. It mainly studied on physiological-ecological characteristics of mixture grasslands composed of different Medicago varia Martin and Bromus inermis, the influence of fertilization and clipping on these characteristics, and the interspecies competition in mixture communities. The purpose of thi...