Abstract: In this paper, the species and life form diversities of fourteen main communities in South Songnen Plain and the relationship between species diversity and community succession are analysed by using Margalef and Menhinick richness indices(R₁, R₂ ), Hill cliversity indices(N₁,N₂) and Pie1Ou evenness index(E). The results show that the species diversity and richness index of Leymus chinensis-Potentallia flagellaris community distributed on lowland are thehighest, those of Ulmus Pumila, Stipa baiclensis, Stipa baiclensis + Filifolium sibiricum and Stipa grandis communities distributed on dunes are the second. while the corTununities distributed on alkalized meadow, such as Suaeda corniculata, are the lowest. Communities with higher species diversity have a higher life form diversity. The species diversity index of Anenrolepidium chinense community is situated at the stage between initial and middle successional series.

Key words: Community, Species diversity, Succession, Songnen Plain, clay, organic matter, soil compression-rebound, shear strength, triaxial test, oedometer test