Abstract: In the returning farmland to grassland in the farming pastoral ecotone of Siziwang Banner in Inner Mongolia,four different types of soils were investigated by using line transects method.The four types were the plant communities of chestnut soil,brown calcic soil,gray-drab soil and meadow soil,and the characteristics studied included the plant community structure,species composition,the ecological type of plant water,α-diversity and community stability.The results showed that the number of species decreased gradually from simple to complex,and tended to stabilize after returning farmland to grassland with the increase of years upon returning from farmland.Chestnut soil,brown calcareous soil and gray-drab soil were dominated by typical xerophytes,and meadow soil was dominated by xerophytes.The plant diversity of chestnut soil was slightly higher than that of brown calcic soil,gray-drab soil and meadow soil.The community stability of brown calcic soil was higher than that of other three soil types,and there was no obvious relationship between the stability and diversity of plant communities in the four soil types.Therefore,it is important to protect the plant diversity in the farming pastoral ecotone for the development and rational utilization of the desert steppe farming pastoral ecotone.

Key words: Farming pastoral ecotone;Returning farmland to grassland;Soil types;Plant diversity