Abstract: Aiming to well understand the relationship between environmental factors and the structure and distribution pattern of plant communities in inter-dune lowland of the Mu Us Sandy Land, this study took vegetation complex of inter-dune lowland in the Mu Us Sandy Land as research object and made a classification and ordination analysis to plant community using the two-way indicator species analysis (TWINSPAN) and principal component analysis (PCA), and detrended canonical correspondence analysis (DCCA) to soil environment factors based on field plant community investigation. The results showed that there were 53 plant species which were classified into 21 families and 46 genera. The dominant families were Compositae (11 species), Gramineae (7 species), Cyperaceae (7 species), Leguminosae (5 species), and Chenopodiaceae (4 species), which respectively accounted for 20.8%, 13.2%, 13.2%, 9.4% and 7.5% of total species amount. Perennial herbages and mesophyte were the most abundant ecotype. The 67 investigated plant community quadrates were divided into 17 groups by TWINSPAN, and finally determined as 21 associations according to the community characteristics. The PCA analysis showed that the first ordinate axis mainly expressed the communities dominated by Salix psammophila, Calamagrostis pseudophragmites and Puccinellia tenuiflora, and the second ordinate axis mainly expressed the communities dominated by Carex duriuscula. The DCCA ordination indicated that the main ecological factors that affected the distribution of plant associations were ground water level and soil Ca²⁺, K⁺ and Na⁺ content. Our results will provide scientific basis for reasonable management, utilization and restoration of inter-dune lowland pasture of the Mu Us Sandy Land.

Key words: Mu Us Sandy Land, DCCA, PCA, classification, ordination