Abstract: Temperate Ulmus pumila sparse forest grassland ecosystem in Inner Mongolia Plateau is a special ecosystem in China, and even in the world. Its study is of significance in deeply understanding the vegetation distribution patterns in the earth, and favoring the protection of this ecosystem. In this paper, the geographical distribution, species composition, community structure, and natural regeneration of this ecosystem as well as the related climate and soil conditions were analyzed, and a comparison on the characteristics of this ecosystem with those of grassland- and forest ecosystems was made. It was indicated that the temperate U. pumila sparse forest grassland ecosystem in Inner Mongolia Plateau could be regarded as a kind of longitudinal zonal (water gradient) climax vegetation formed under unique climate, soil and topographic conditions. The key factors deciding its existence were annual precipitation and soil moisture, while sandy soil was the secondary factor. This ecosystem was neither forest nor grassland, but a transition between them. In our opinion, The Vegetation of China should add a new vegetation type, temperate sparse forest grassland.

Key words: Sophora davidii community, Dominant population, Niche breadth, Niche overlap, Loess gully region