Abstract: In this paper, the dynamic changes in bacterial and fungal community structures in the rhizosphere of cucumber in different cropping seasons were analyzed with the terminal restriction fragment length polymorphism (T-RFLP) method. Results showed that the diversity index of bacterial community decreased from the first to the seventh cropping season, and then increased in the ninth cropping season. At 50 days after sowing, the diversity index of fungal community increased from the third to the seventh cropping season, and then decreased in the ninth cropping season, which was in contrast with the trends observed at 30, 40 days after sowing. The number of predominant bacterial species decreased from the first to the seventh cropping season and then increased in the ninth cropping season, and the predominant species mainly included classes such as Clostridia, γ-Proteobacteria, α-Proteobacteria and unknown bacteria. The number of predominant fungal species increased from the first to the seventh cropping season, then decreased in the ninth cropping season, and the predominant species mainly included Hyphomycetes, ectomycorrhizal fungi, Zygomycete, Agaricomycetes, Basidiomycetes and unknown fungi. Moreover, the influence of cucumber growth stages on soil bacterial and fungal community structures was stronger than that of cropping seasons. In conclusion, continuous cropping changed the cucumber rhizosphere bacterial and fungal community structures and diversities. Especially, the bacterial and fungal community structures in the seventh cropping season were obviously different from those in the other cropping seasons.

Key words: Schima superba, neighbor competition, growth, root plasticity, provenance