Abstract: Based on the data of adjacent lattice method, vegetation characteristics such as species importance value, niche breadth, niche proportional similarity and niche overlap value were measured in the waterlevel fluctuation zone (WLFZ) and nonfluctuation zone (CK) of the canyon landform area of the Three Gorges Reservoir. The niche characteristics of dominant plants were studied and their forming mechanisms were discussed through the comparison between the WLFZ and the CK to provide a theoretical basis for optimal plant selection and scientific plant configuration of vegetation restoration and reconstruction in the WLFZ. The results showed that: (1) 10 dominant plant species appeared after experiencing many times of water level fluctuation in the WLFZ. Among them, Eclipta prostrate had the biggest niche breadth, followed by Digitaria chrysoblephara, Bidens pilosa, Setaria viridis, Echinochloa crusgalli, S. glauca, Xanthium sibiricum, Cynodon dactylon, Cyperus rotundus, and Polygonum hydropiper. The larger niche proportional similarities in the WLFZ were D. chrysoblephara vs. E. crusgalli, E. prostrata vs. X. sibiricum, B. pilosa vs. P. hydropiper, and the larger niche overlap values were B. pilosa vs. P. hydropiper, E. prostrata vs. X. sibiricum, C. dactylon vs. C. rotundus, D. chrysoblephara vs. E. crusgalli. These results suggested plants with larger niche breadth had larger niche proportional similarity and niche overlap value. (2) The proportion of niche proportional similarity and niche overlap value of more than 0.5 were 51% and 67% in the WLFZ, but 31% and 44% in the CK, respectively. The niche breadth, niche proportional similarity and niche overlap value of most dominant plants in the WLFZ were greater than those of the same plants in the CK, which indicated that the niche differentiation between different dominant plants was lower, the interspecific competition was more intense, and the stability of plant community was worse. (3) The biological characteristics of plants and their adaptabilities to  the environmental changes, and the habitat stability were the main reasons for the differences of niche characteristics between the WLFZ and the CK.

Key words: Alternaria longipes, phylogenetic analysis, 16S rDNA sequencing, biocontrol., endophytic bacteria of root nodules