Abstract:To explore the coupling relationship between forest community characteristics and species diversity, three typical communities (Pure forest of B. pendula [PFB], we selected Mixed forest of B. pendula with Populus laurifolia [MFBP], and Mixed forest of B. pendula with Salix alba [MFBS]), in brich forest national forest park Irtysh river, to survey the community characteristics (height, tree bole height, diameter at breast height, crown width, coverage, and others). According to these indices, richness index, diversity indexes and evenness indexes were calculated, and canonical correspondence analysis (CCA) was performed. The results showed that: (1) the maximum height and clear tree bole height of the arbor layer and the canopy coverage and ground diameter of the shrub layer all occurred in MFTS; there were significant differences in the herb layer (except base diameter); the herb coverage of the MFBS was 19.1% and 51.8% higher than that in the MFBP and PFB. (2) In three different forests, the important value of Betula pendula in the arbor layer was maximal, and the dominative species in the shrub layer were Rosa laxa and Crataegus altaica, and that in the herb layer was Carex bohemica. (3) The mean species richness, Simpson index and ShannonWiener index of the arbor layer and Pielou index, Alatalo index of the shrub layer showed the same pattern, i.e., MFBS > MFBP > PFB. However, the herb layer exhibited a different order, not include Alatalo index, with PFB > MFBP > MFBS (P > 0.05). (4) CCA showed that the correspondence associations between community characteristics and species diversity differed among the three forest types. In the pure forest of B. pendula, tree clear bole height, the height and crown width of the shrub, height of the herb had the highest impact on species diversity. In the mixed forest of B. pendula with Populus laurifolia, the height and crown width of the tree, shrub crown width and herb height had the highest impact on species diversity. In the mixed forest of B. pendula with Salix alba, the DBH, the crown width and coverage of the shrub, the height of herb had the highest impact on species diversity. The results showed that for all three forests the characteristics of the tree clear bole height and crown width of the shrub and herb height had a substantial influence on plant species diversity.