中文摘要：

内蒙古高原分布的温带榆树稀树草原生态系统在中国乃至世界上都是一种特殊的生态系统，对于它的研究可加深对植被分布规律的理解，且有利于该系统的保护。本文分析了该生态系统的地理分布、气候特点、土壤状况、物种组成、群落结构及天然更新状况等，比较了草原、森林和稀树草原3个生态系统的特征，提出了在内蒙古高原分布的温带榆树稀树草原生态系统是在独特的气候、土壤和地形条件下形成的经度（水分梯度）地带性顶极植被，决定其存在的最关键因素首先是降水量和土壤的水分条件，其次才是沙质土壤。这种生态系统既不是草原，又不是森林，而是介于落叶阔叶林和草原之间的一种生态系统类型。在此纬度带上，从东到西分布的经度地带性植被谱应为：温带森林、温带稀树草原、典型草原、荒漠草原等。在同一纬度带上，沙质土壤的基质并不完全被稀树草原生态系统所覆盖，还有沙漠等生态系统类型。建议《中国植被》增加一个新的植被类型，温带稀树草原。

英文摘要：

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.